















V * 


C* .v'l 


f A° 






<£ i* * -4. 




'■j- V 


; - a % - .o'*- - *-..; - \a : 

^ -'^V' ■ 0 *£(&*,* % ■»' <% 

V O <r ? -< V- V C t 


CO 

,x -K 


x OC. >. ^ -y * f = \° ^. >• ^ 

* ‘T, . Jr " vS 'Cf. , > * *t 

°o * ^ **'**>*'■& °o ", 

^ * * o /■ ^ * \} S S * * ? ft > S *9^ 9- ' • 0 t ^Q' l 

* . V ** A-. .*> ^ 


fi ^ ~ ^ V * 

jv\ |g \ o ^ ,.^> -- 

^w\fr#/ i- 7 ' -» 


^ ^ * ;• vj&kIOl - 


c z : *v * - ! 

* V ^ ^ • <^V' -A - ^ * .,V 


*«*\* «v <r^ v - % * *>+ 

** . . x ,y ^ y o • k ^ O ^ ^ <s ^Vj» 

* n *. * 1 * * <p J> t 0 s c * *c cv • 

^ 0 \ ~ (&nSS<». * +*■ Y » - : >.«^ ' '"o . <R 


CO 


^ V ^nSj> > * ~ * ^5 iLjr/* ^ % ’ 

rO * * A r% ^ «-^C^ v x O' ✓ 

s .., e., *.*' ! / •.!>• f ,.., 

.!*♦ > i9‘ * x * 0 ^ c- V . s *f ' 

^ >>. % 1 






■ o 

9 M /» /. v > 




c< 


O « A 


c° N C * 

a v 


o • x 


V'^'V* 

- ** o°V;;*/% . 

✓ . V Jf r r + >\ -A' 

^ -V 1 V ^ yV/^/ *^» \v 

_o oo' - -< ^ > 

X 0 >- s£ 

- 

- 




A 


^ o ^ * 


V ^ 


7I|U# ^ \ 

.V 


.-.s ' 5 ^ 


> C 

, __... _ _ S 

^ ^V^VvsA. » \ \ ._p 


A* « ^ 

0° *£$p£ 


^ /\ O, '* M c S 

A*' C»' C %. " .0^ ,« 

V ^ « c-^XV ^ •-> 0 v' ^ 



if 







C‘ * v 

* n ^ *«11 
0 /■ C 1 

r 'V \V * 

° °^> ^ * 

- 3 » V 


* U * 

^ 4kN ^ ' 

^ K ® 4 ■• 

x 0 o > 

o ’> . 

s. + 

V °rf> * „ ^ ,* ~Q. IT „ ,j 

? s s * * T x, V 3N ° * * * 0 r J b 

- a*' ^ r ^„V *<* 1 

$ 'Kr Cl - ^ -JXAafiT ^ 

^ <0 



■ 0> V *<r> 

* ^ V 1 

^ ^ A A c*v x y. 

y 0 . * /V ^ ^ 

A\ c 0 N C * *© 

> < O * _Cv£N^ ^ O 

*^. «aN 

^ t *■*■ v r 


6 6 ^ 




O' 

^ * 0 /• 


J5 * 


'« %■ *& 


£ 


V </\ 


lV < 


• '/.* • • • S^'/y ^'.% 


v<> 


0 \ ' 


£ ^ V 
* °' #' *%• '* 


3 N 0 


V 


*7-' 

/U ° <?* <Y> 

k\ *+ .<? 


*v 4 > %, - 

-* c t* s 

J 0 . X * A ^ * 

\ 0 W G . <V 


n_ O 

n> o <f' 

% T * 


A c 0 N G * 

1 *f> 


CT v 


v i 




a ^ 


or, 


o5 ^ 

^ o • <£> j 

^ *3 


* 

C)_ ^ 'S Cl 

O'- ,.'*», -% ’" v\s^^."> 

*• y *''j<\ < I#A. ^ ^ 


lV <p. 


y * 




0 * \ 


O 1 


H V 


,0 o 


\ ^ 


-O -» **>' 

,% * , ' , v'.''V'* > 

V -■■ * 


<f> 


aV 





- ^0 o ^ 

,*> ^ » 
o> *o, cv 

•v ^ - *■ 






















Mason Regulator Company Series, No. 4 



What an Engineer Should 
Know about Electricity 


BY 


ALBERT L. CLOUGH, E.E. 

1 » 


Also the Rules and Requirements of the 
i Underwriters’ International Electric 
Association, for the Installation 
of Electric Light and Power 


PRICE, FIFTY CENTS , 


JUN 18 ‘334 | 


* Of W AS"' 


PUBLISHED BY 3 

THE MASON REGULATOR COMPANY 

Boston, Mass. 




OA 


COPYRIGHT 

1894 

BY THE MASON REGULATOR COMPANY 5 
BOSTON, MASS. 




INTRODUCTION. 


The development and extension into practical use of 
the various electrical devices, have left extremely few 
buildings, Whether factory, office building, or residence, 
unequipped, to a greater or less degree, with the modern 
time and labor saving and comfort increasing arrange¬ 
ments to which electricity seems specially adapted. Elec¬ 
tric bells, gas lighting, and burglar alarms are found in 
most well equipped residences, and the incandescent light 
in not a few ; while the applications in factories and public 
buildings of all kinds are far more various, including 
watchmen’s clocks, incandescent and arc lights, tempera¬ 
ture regulators, annunciators, automatic fire alarms, pri¬ 
vate telephones and telegraphs, and electric fans and 
elevators. 

We have grown to depend upon these conveniences so 
implicitly that an instance of their failure is particularly 
annoying; yet it must be confessed that the liability of 
imperfect operation in most of them is still quite large, 
due in great part to the careless way in which many of 
them were installed in the period of hasty construction 
which elapsed, before electricity had become the indispen¬ 
sable reality which it is to-day. 

The presence of some one able to remedy minor elec¬ 
trical troubles, and especially to tell whether electrical 
construction work is being, or has been, well done, is a 
very great advantage, and is capable of preventing much 
future trouble and financial loss. 


l 



2 


INTRODUCTION. 


The object of this book is to present plainly, and with¬ 
out the use of difficult technicalities or mathematics, to 
all who have to deal with electrical appliances, brief de¬ 
scriptions of their various forms, practical “pointers 11 on 
the troubles to which they are liable, and their reme¬ 
dies, as well as general instructions for doing simple 
construction work such as is often needed as a slight exten¬ 
sion of an already established plant. It does not make 
any claim to cover the whole field of electrical construc¬ 
tion, but presents some hints which it is hoped may be 
useful. 

There is one matter which should be at the outset fully 
appreciated and always kept in mind, and that is, the 
necessity for the use of the best materials and the employ¬ 
ment of the best workmen in order to secure the best 
results. This is true in electrical engineering as nowhere 
else. It is simply impossible to secure good, uninter¬ 
rupted service, unless the conditions have been made 
favorable by the most thorough-going construction in 
every particular, however minute. Electrical work cannot 
safely be slighted. 

The Fire Underwriters have done much in the direc¬ 
tion of improved electrical engineering. Their rules for 
the installation of electrical apparatus in buildings which 
they approve are very excellent, and should be strictly 
followed by every one concerned with electric light or 
power work. 

• It will be noticed that the matter to be treated here has 
been placed under the two heads of light current working 
and heavy current working , a classification which it is 
believed will be useful. A few general considerations 
regarding electricity precede. 


Albert L. Clough. 


ELECTRICITY FOR ENGINEERS. 


GENERAL CONSIDERATIONS. 

Source of Electricity. Electricity for its various uses 
is furnished by either the battejy or the dynamo machine. 
In the case of the battery it is the result of chemical action, 
while in the case of the dynamo it is the result of the ex¬ 
penditure of mechanical power. 

An electrical circuit is the continuous path of an elec¬ 
tric current. For the current to flow, it must have what 
is called a complete or closed circuit. It must be a contin¬ 
uous path including the battery or dynamo, the wires, and 
all the devices to be operated. We may always start at 
any point in a circuit, and trace the path of the current 
entirely around back to the starting point. If we cannot 
do this there is a break somewhere, and the circuit is said 
to be open. 

A conductor is any body that will form any part of a 
path or circuit for the current, and an insulator is one 
which will not form a path for it. The best conductors 
are the metals and carbon ; while air, glass, porcelain, and 
rubber are among the best insulators. 

Whenever the current passes a more or less number of 
times through a wire in the same direction about a piece 
of soft iron, the iron becomes a rrtagnet as long as the 
current is flowing in the wire, but ceases to be a magnet 
when the current stops ; indeed, the wire itself has all the 

3 



4 


ELECTRICITY FOR ENGINEERS. 


properties of a magnet, which the presence of the iron 
simply increases. The iron, with the wire round it, is 
called an electro-magnet , and will attract other iron held 
near it. 

Heat is always produced throughout the circuit when 
the current is flowing, but especially when the current 
meets with a hindrance or resistance to its flow, as when 
it comes in its path to a rather poor conductor. The 
heating is then mostly produced at the points in the cir¬ 
cuit where the poorer conductors are situated. For in¬ 
stance, the heat appears at the filament of an incandes¬ 
cent lamp rather than along the wires which feed it, owing 
to the fact that the filament, because of its very small size 
and the material of which it is composed, offers many 
times as much resistance to the current as does the whole 
length of wire leading to it. 

VOLTS, AMPERES, AND OHMS. OHMS LAW. 

While it is unnecessary for one to have an extensive 
theoretical knowledge of electricity to successfully deal 
with electrical apparatus, a thorough knowledge of the 
practical units of electrical measurement is essential. The 
terms volt , ampere , and ohm are so constantly used by 
all electricians in describing and rating the various motors, 
dynamos, lamps, batteries, and other electrical machinery, 
that they should be perfectly clear to anyone who aims 
at an intelligent understanding of the devices with which 
he may meet. 

In any electric circuit we have to consider three condi¬ 
tions. (1) The volume, strength, or intensity of the cur¬ 
rent ; (2) its # tension or electromotive force (e. m. f.), 
which is the pressure that causes the current to flow; and 
(3) the resistance of the circuit, which is the hindrance to 


GENERAL CONSIDERATIONS. 


5 


the current’s flow. The current strength is measured in 
amperes, the pressure in volts, and the resistance in ohms. 

If we know any two of these three facts concerning a 
particular circuit, we may find the third by a very simple 
formula. For instance : if we know the current passing to 
be a certain number of amperes, and the pressure that is 
forcing the current along to be a certain number of volts, 
and we wish to find how much resistance the circuit is 
offering to the current, we have only to divide the num¬ 
ber of volts by the number of amperes. The result is 
the number of ohms. 

And again, to know how many volts pressure it will 
take to drive a certain number of amperes of current 
through a circuit whose resistance is a certain number of 
ohms, we simply have to multiply the number of ohms 
by the number of amperes, the product being the required 
pressure in volts. Or, if we know how many volts pres¬ 
sure is being applied to a circuit, and how many ohms 
resistance it is offering, dividing the number of volts by 
the number of ohms will give us the number of amperes 
of current flowing. 

The actions in an electric circuit are often compared 
with those in a system of city water distribution: the 
electrical pressure, or electromotive force corresponding 
to the head of the water, the electric current to the flow¬ 
ing of the water, and the electrical resistance to the fric- 
tion of the piping and the contractions at the outlets. 
Sometimes it is helpful to bear this illustration in mind. 

As an example of one of the foregoing rules, suppose 
we have a 110 volt incandescent lamp, that is, a lamp 
intended to be run at a pressure of 110 volts, and we 
know its resistance to be 200 ohms; how much current 
will pass through it when in use? 

110 -r 200 = .55 amperes, is the correct answer. 


6 


ELECTRICITY FOR ENGINEERS. 


The presence of an electric current means that there 
has been expended for its production a certain amount 
of energy or power, whether by the dissolving or burning 
of zinc in a battery or by the combustion of coal under a 
boiler. The heating of an incandescent lamp filament 
is nothing more or less than the return, in the same 
form, of a part of the energy or power which was given to 
the boiler as the heat of the burning coal, and which was 
used by the engine and dynamo in the production of 
the current; and the operating of a street car motor is 
simply the giving back of part of the mechanical power 
which was expended at the power house in running the 
dynamos that feed the circuit. The power in an electric 
circuit is measured in horse-power. The number of 
horse-power being given out is found by multiplying the 
pressure in volts by the current in amperes, and dividing 
the product by 746. If the product is left without divid¬ 
ing by 746, we have the power in watts, a unit which is 
much used in the rating of electric lamps, and some¬ 
times even in stating the capacity of dynamos. One or 
two examples may be useful here. 

A dynamo is delivering a current of 10 amperes at 2500 
volts to some arc-lamps, how many horse-power is it de¬ 
livering? 

10 x 2500 ~r 746 = 33.5 HP (about) ; answer. 

An incandescent lamp is taking .55 amperes at 110 volts 
pressure, how many ivatts is the lamp consuming? 


.55 x 110 = 60.5 is the result. 




LIGHT CURRENT WORKING. 


7 


PART I. 

LIGHT CURRENT WORKING. 

THE BATTERY. 

The battery is indispensable to all branches of applied 
[electricity in which small currents are used, as is the case 
in all kinds of signalling, gaslighting, and the like. A 
[battery is an arrangement for producing available elec¬ 
tricity from chemical action, and it always consists in 
practice of a plate of zinc, and a plate of some other metal 
or of carbon, both immersed in a chemical solution in a 
convenient jar. Each one of these combinations of the 
two plates, solution, and jar is generally called a cell, 
while the term battery is reserved for a number of cells 
connected one to the other. When a circuit is completed 
between the two plates in a cell, a current flows, due to an 
electromotive force or difference of electric pressure of 
from 1 to 2 volts which is set up between them : the zinc is 
dissolved and gradually disappears into the solution, while 
the solution is altered chemically in various ways. 

Certain types of cells make use of two solutions in their 
operation, the two different fluids being kept from mixing 
by porous earthenware partitions. In such cases the so 
lution surrounding the zinc is useful in attacking and 
dissolving it, while the other fluid acts to prevent the 
accumulation of gas bubbles upon the other plate which 
would otherwise produce polarization, or a checking of 
the battery’s action. In certain cells there is a block of 
some material placed on the copper or carbon plate, or it 


ELECTRICITY FOR ENGINEERS. 


is surrounded by a paste, in order to prevent polarization ; 
this being used instead of a second solution. 

There is practically but one way of connecting cells to 
form a “ battery. 11 This is to connect, by wires, the zinc 
plate of one cell to the carbon or copper plate of the next, 
and so on; so that no matter how many cells one has, 
when joined in this way, there will be an unconnected 
zinc at one end of the Series and an unconnected carbon 
or copper at the other end, and from these two free ends 
wires go to the instruments to be operated. Other methods 
of connection suitable for exceptional instances will be 
found in text books on the subject, 

Of course a battery, like all other parts of a circuit, offers 
resistance to the current, and this fact should always be 
borne in mind in any calculations on the subject. The 
resistance which a cell offers may be roughly stated as 
from | to 2 ohms, and depends largely upon the nature of 
the solution, and is larger as the plates are smaller andj 
farther apart. The resistance of a battery of several cells< 
is naturally the sum of the resistances of the separate cellsj 
and its electromotive force is the sum of the electromo-i 
tive force of the separate cells. 

Example : —How much current will a battery of 6 cells 
force through an electromagnet of 5 ohms resistance, not; 
counting the resistance of the connecting wires. The! 
electromotive force of each cell is 1.5.volts and the resist 
tance 1 ohm. 

6 x 1.5 = 9.0, or total electromotive force. 

6x1 =6.0, or resistance of battery alone. 

6 + 5 =11, total resistance in circuit, 

9.0 = .818 amperes ; answer, 

IT 


LIGHT CURRENT WORKING. 


9 


KINDS OF BATTERIES. 

Although there have been devised an almost endless va¬ 
riety of batteries, there are comparatively few much used, 
and with which one is likely to meet; these are 

The Leclanch6 ; and other sal-ammoniac cells. 

Gravity and other blue vitriol cells. 

Bichromate and other cells for occasional use. 

The Leclanche Cell is one of the most important ele¬ 
ments in the success of the modern “ light current” appli¬ 
cations of electricity. It is difficult to imagine how we 
could get along without it, as it operates nearly all the elec¬ 
tric bells and other signals, does practically all the electric 
gaslighting, and forms a part of every telephone outfit; 
indeed, it is such a widely used and well known article as 
hardly to need description. In this battery an amalga¬ 
mated 1 zinc rod and a carbon plate are employed, placed 
in a solution of sal-ammoniac. The sal-ammoniac acts 
upon or dissolves the zinc, while a mixture of black oxide of 
manganese and powdered coke placed about the carbon 
prevents polarization. 

The Leclanche cell is made in two general forms, the 
porous-cup or disqtie, and the prism or Gouda. In the 
porous-cup form the black oxide of manganese and coke 
are kept in place about the carbon by a porous earthenware 
jar, and in the gonda the mixture is compressed into 
solid blocks, one of which is attached to either side of the 
carbon plate by rubber bands; of these two varieties 
the gonda is probably of the lowest resistance. Of late, 
[cells have been considerably used in which the zinc, in¬ 
stead of being a rod, is‘in the form of a hollow cylinder 

1 The method of amalgamating or coating zinc with mercury is simply to 
■ clean the zinc with muriatic acid and then rub it with a few drops of metallic 
! mercury. 




10 


ELECTRICITY FOR ENGINEERS. 


surrounding the carbon and its depolarizing mixture, 
securing very low resistance. Even if the depolarizing 
mixture is not used at all and the cell constructed simply 
of the zinc and carbon plates in a sal-ammoniac solution, 
it works very well for ordinary purposes, and quite a 
variety of forms are made after this plan. All good cells 
of this class have glass jars with tightly fitting covers 
through which the zinc and carbon pass snugly, thereby 
preventing too rapid evaporation of the liquid. 

It is always to be remembered that the Leclanch6 cell 
is only suitable for applications that require a rather small 
current intermittently; that is, for circuits which are kept 
open most of the time, and in which the apparatus acts 
when the circuit is closed, as is the case with electric 
bells, gaslighting, and the like. It is distinctly not appli¬ 
cable to closed circuit work. 

The fact that in this cell the consumption of zinc and 
the chemical change of the solution occur only when cur¬ 
rent is being generated and not when the circuit is open, 
is one of the great advantages, and under ordinarily good 
circumstances it should run for years without any con¬ 
siderable amount of care. The quickness with which it 
will “run down” and require attention depends mostly 
on how long, in all, the circuit has been closed, so that 
a few hours continuous closure might exhaust it as much 
as years of ordinary service. The thing to be avoided is 
accidentally allowing the circuit to be closed for a long 
time. Directions for “ setting up ” usually accompany 
these cells, but a few points not always mentioned may 
be useful. One should always be sure that there is no 
possibility of the zinc coming into contact with the carbon 
or its attachments in the liquid, as this would run the cell 
down rapidly, and one should see that the rim of the jar 
and the head of the carbon are completely covered with a 


LIGHT CURRENT WORKING. 


11 


thin layer of paraffine wax, and that the jar is always kept 
between one-half and two-thirds full of solution. It is a 
very common mistake to fill the jars too full: in which 
case, if the paraffine rim is not perfect, the solution is 
almost sure to crawl up the glass and reach the connec¬ 
tions of the carbon and zinc, corroding them, sometimes 
to the extent of breaking the circuit, as well as dampen¬ 
ing the shelf upon which the cells rest, thus causing an 
excape of current and a gradual exhaustion of the battery. 
In locating a battery intended for permanent use, it is 
best to place it where it is neither too hot and dry nor very 
damp, as rapid evaporation of the liquid in the first in¬ 
stance, and corrosion of the connections in the latter, are 
apt to follow. It is bad practice, on the whole, to place 
it in a furnace-heated basement, for the air is too hot and 
dry in the winter and too damp in the summer. About 
the best place seems to be on a shelf in a closet near the 
middle of the ground floor of the building, as it is very 
accessible and at a nearly even temperature. Of course 
a battery should never be located where there is any 
possibility of a freezing temperature being reached. 

In spite of every precaution, the circuit of a battery will 
sometimes become closed for a long enough time to ex¬ 
haust it. If the zincs are seen to be very much eaten 
away and the carbon and its attachments covered with 
crystals, and if there is a smell of ammonia noticeable 
about the cells, one may be pretty sure that this has hap¬ 
pened, and that the battery will probably have to be 
removed. The first thing to be done is to disconnect 
from the battery the circuit on which the trouble has 
taken place, and sometimes, if the exhaustion has not 
srone too far, the batterv will, if left to itself for a few 
days, recover almost its original strength. If, however, 
it does not, the cells should be taken down and taken 


12 


ELECTRICITY FOR ENGINEERS 


apart, all the parts washed, and the crystals scraped off; 
the zincs, if not too much eaten away should be amalga¬ 
mated, and a new solution made of the best sal-ammoniac. 
The carbons have not been injured, but the gondas or 
the contents of the porous cups have been rendered use¬ 
less. However, these can be made almost as good as 
ever, and the expense of buying new ones avoided if they 
are treated in the following way. Put the cells together 
again, having them still joined in series; replace the sal- 
ammoniac solution with water, and to each jar add half 
a fluid ounce of sulphuric acid; then connect the battery 
to a dynamo circuit so that the current enters at the 
“ free ” carbon pole and passes out at the “ free ” zinc. 
It will generally be necessary to put quite a large amount 
of resistance, either of wire or of incandescent lamps, in 
circuit with the cells, so that the current will not be too 
strong. 'Have the current pass in such a direction, and 
of such a strength, that gas bubbles will be given off pretty 
-freely at the zincs, but very slightly at the carbons; and 
pass the current for six or eight hours. 

The important point is to have the current in the right 
direction; that is, so that the gas will be mostly given 
off at the zincs. Of course the current of an alternat¬ 
ing dynamo would not do for the purpose. After the 
cells have been so treated they are ready for the fresh 
sal-ammoniac solution and newly amalgamated zincs, and 
should be found to be as strong as ever. 

I might say here that sal-ammoniac, although harmless 
to the person or to the clothes, attacks copper or brass 
very vigorously, so that a single drop spattered upon a 
wire is likely to eat it off completely and open the circuit, 
a trouble which is very annoying and difficult to locate. 

Gravity and other Blue Vitriol Cells. — Practically all 
closed circuit working employs cells of this class. By 


LIGHT CURRENT WORKING. 


13 


closed circuit working is meant the use of circuits contain¬ 
ing devices which are operated upon the breaking of the 
current which is kept continually flowing. This includes 
local commercial telegraph lines, the police and fire alarms, 
district telegraph, some burglar alarm systems, etc. These 
cells always consist of a zinc plate in a solution of zinc 
sulphate or white vitriol, and a copper plate in a solution 
of copper sulphate or blue vitriol. The zinc sulphate acts 
upon zinc and gradually dissolves it, while the copper sul¬ 
phate about the copper prevents polarization (q.v.). The 
two solutions are sometimes kept from mixing by the use 
of a porous cup, as in the Daniels cell, or are kept apart by 
gravity, as in the gravity cell. The gravity cell consists 
of a large cylindrical jar on the bottom of which is placed 
a +, made of sheet copper stood on edge, and provided 
with an insulated wire leading up and out of the jar ; from 
the edge of the jar is suspended the zinc in a horizontal 
position near the top of the vessel. The zinc may be 
either in the form of a wheel or any shape giving large 
surface. The copper sulphate solution being heavier than 
the zinc sulphate solution, sinks to the bottom of the ves¬ 
sel, forming a layer about the copper plate and preventing 
polarization, and leaving the upper part of the jar about 
the zinc filled with the lighter zinc solution. The best way 
of “ setting up ” the gravity cell is to place at the bottom 
of the jar around the copper about one pound of blue 
vitriol, then to add one ounce or so of white vitriol, 
and finally to fill the jar with water sufficient to cover the 
zinc. The solutions should separate, and the cell be ready 
for use in a few hours, especially if it be short-circuited; 
that is, if the wire from the copper be attached to the zinc. 
If the white vitriol is not at hand, the cell may be started 
by simply supplying the blue vitriol and water, and short- 
circuiting the cell. The solutions will separate in a day 
or two. 


14 


ELECTRICITY FOR ENGINEERS. 


In maintaining the gravity cell the line of separation of 
the two solutions should be kept an inch or two above 
the copper, and in no case should it approach the zinc. 
If one has any considerable number of these cells to take 
care of, it is well to be provided with a good-sized battery 
syringe and to keep a saturated solution of blue vitriol on 
hand. It is desirable, too, to have a hydrometer —a little 
floating instrument for determining the strength or den¬ 
sity of the zinc solution. It is the tendency of the zinc 
solution to become too strong or dense, after the cell has 
been working some time, in which case ope should remove 
some of it by means of the syringe and replace it with 
water until the hydrometer, when floated in the solution, 
stands at about 1020 degrees. If this were not done, the 
zinc solution might become denser than the copper solu¬ 
tion, which would result in the two solutions changing 
places and stopping the action of the cell. There should 
always be crystals of blue vitriol at the bottom of the jar to 
keep the blue solution saturated ; but in case all the crystals 
become dissolved and the blue solution gets low, it can be 
replenished by means of the syringe without causing the 
liquids to mix, and a fresh supply of crystals may be 
dropped into the jar. Once in a while the jars should be 
thoroughly cleaned out and set up anew, but this is only 
necessary at long intervals. The zinc in this class of cells 
never requires to be amalgamated. 

The bichromate cell is very little used for purposes that 
require continuous service ; it is mostly employed for oc¬ 
casional uses, as the operating of medical batteries and 
experimental apparatus of all kinds. This cell makes use 
of the zinc and carbon plates in a solution for which the 
following is a recipe: — Add pulverized bichromate of 
soda to warm water until it will dissolve no more ; allow it 
to cool, and then add one-fifth of its volume of common 


LIGHT CURRENT WORKING. 


15 


sulphuric acid. When the cell is set up with this solution 
its electromotive force is quite high, and its resistance 
fairly low, so that it will give quite a large current if it is 
not required for a long time. The zincs, however, require 
to be frequently amalgamated, and must not be left in the 
solution when the cell is not in use, as they rapidly dis¬ 
solve even when the circuit is open. The soaking of the 
carbons in melted paraffine to prevent the possibility of the 
solutions reaching the connections is also an important 
precaution to be observed. For further particulars in re¬ 
gard to cells of all kinds, the reader is referred to an 
excellent work entitled “ Electric Batteries,” by Alfred 
Niaudet, which gives full description of all the various 
types. 

CIRCUITS. 

As is well known, copper wires of various sizes are 
employed in electrical work, the numbers used in this 
country to designate them being those of the American, 
or Brown & Sharpe, wire gauge. 

The tables published by the various wire manufacturers 
contain the diameters, sectional areas, the resistance in 
ohms per thousand feet, feet per ohm, ohms per pound, 
and feet per pound of the sizes designated by the different 
gauge numbers. These tables may be obtained of the man¬ 
ufacturers upon application, are very useful, and should 
be in possession of everyone having to do with electrical 
apparatus. It may be well to be reminded that of course 
the resistance of a circuit is proportional to its length,— 
a circuit twice as long as another composed of the same 
sized wire offering twice as much resistance ; and also that 
a circuit of a certain gauged wire possesses one-half the 
resistance of one of the same length formed of wire having 
twice the sectional area of the first. The sizes most used 



16 


ELECTRICITY FOR ENGINEERS. 


for “ light current working 11 in buildings have been Nos 
18 and 16; but some of the best electricians are nov 
using 16 and even 14, as being larger and less likely to b( 
broken. No. 18 or 16 wire which has been insulated b} 
winding it with a double layer of cotton thread and ther 
soaking it in melted paraffine is called annunciator wire 
and that which has a layer of braiding over the winding 
is generally spoken of as office wire. These forms o: 
insulation are the ones almost universally used for lighi 
current work, and, although good enough when kept dry, 
should not be depended upon for use in damp places, as 
the moisture works through the covering, causing ar 
escape of current to take place which gradually exhausts 
the battery and corrodes the wire; neither should the} 
be employed where there are corrosive fumes of any sort 
as they do not protect the copper from being acted upon 
In such cases as these, one should see that there an 
used wires of the so-called “ weather-proof 11 variety, which 
have coverings treated with water-proofing and fire-proof 
ing compounds. Some of the most careful and thorough 
electricians are using these wires very largely in thei: 
best contracts. Whenever the wire is likely to be sub 
jected to hard usage it should have a covering not likeh 
to be worn through or rubbed off. In this respect th< 
braided is far better than the wound covering, and th< 
weather-proof insulation superior to either. A soft rubbe 
tube slipped over the wire at points where it is especiall 
liable to injury is a great protection, and winding it with 
the adhesive insulating tape, especially made for the pur 
pose, has much the same effect. Where wires have to b i 
connected with one another, joints necessarily occur 
They should be avoided as far as possible, and one can b i 
a little forethought and planning arrange so that there will 
be very few required. Formerly people seemed to thinh 



LIGHT CURRENT WORKING. 


17 


jiat any sort of a twisted joint between two wires was a 
Efficiently good electrical connection between them for 
Be of light current circuits; but it is beginning to be seen 
Eat this is the “haste makes waste” policy, and that 
irelessly made joints are almost sure to cause future 
Anoyance and the waste of much time in locating 
oubles. Wherever joints must occur they should, be 
;ade of the regular form of a lineman’s joint in an over¬ 
bad wire ; the wires should be scraped bright and twisted 
ghtly together with a pair of plyers, then soldered, care- 
lily cleaned of any remains of acid, and covered thor- 
ughly with adhesive tape. One should especially see 
lat these precautions are taken with joints that are to be 
mcealed and difficult of access. At this point it may 
C well to speak of the great importance of having only 
ie best connections or contacts in the circuit, so that they 
lay add as little resistance as possible. As every one 
jnows, the connections with almost all kinds of electrical 
bparatus are made by means of binding-posts — screws 
ihich clamp and hold the circuit wires. The wires to be 
onnected to the instruments should always be scraped 
right, and should be placed in the binding-posts so as to 
e least liable to work loose; the surfaces of the screws 
hich clamp the wires ought to be cleaned and should be 
2t up tightly, but not so tightly, of course, as to cut off 
le wire. It is really remarkable how often trouble is pro- 
uced by loose or dirty contacts, and one should ever be 
pon the watch for them. 

The method of supporting the wires is a matter of im- 
ortance ; and I cannot refrain from saying a word here 
gainst the double pointed tack, or staple, which has been 
) much and so injudiciously used for fastening wires in 
osition upon wood-work. Double pointed tacks in care¬ 
ss hands are a fruitful cause of trouble. 



18 


ELECTRICITY FOR ENGINEERS. 


Used in damp places, and driven too hard, they ci 
through the insulation of the wire, increasing the escap 
of the current, or sometimes even cutting off the wire, \ 
which case the remaining insulation holds the severe 
ends very close together and prevents the defect froi 
being readily noticed. Sometimes, in order to save tim< 
more than one wire is held under the same tack, the n 
suit being that a connection is often formed between tw 
or more of the wires and a trouble caused which is ver 
tedious to locate. It is safe to say that staples shoul 
never be used except upon dry wood-work, and then tb 
same staple should never hold but one wire. It is £ 
better to see that they are not used at all, and to insk 
upon the use of the far safer and neater cleat. Thes 
cleats are made of sizes suitable for holding any numbe 
of wires, and may be used with advantage on wood-wor 
or on plastering. They are strips of hard wood intende 
to be fastened in place by screws, and are crossed b 
grooves in which the wires fit tightly when the groove 
side is placed against the ceiling or wood-work and th 
screws set up, the wires being held firmly in place an 
prevented from slipping. They have the advantage ( 
keeping the wires at an equal distance apart at all point; 
thus improving their appearance, besides removing th 
danger of cutting the insulating covering which attend 
the use of tacks. If the wire is drawn taut betwee 
the cleats and all kinks smoothed out of it, and if th 
cleats are placed carefully in line and set up tightly, wine 
ing the wire once round those cleats upon which the mos 
strain comes, a good-looking set of “ lines ” is the result 
but cleat work carelessly done, with the wires sagging an 
the cleats out of line, is an eyesore to every electriciar 
In running circuits in cellars and other damp places, it i 
sometimes best to use small porcelain knobs, screwe 


LIGHT current working. 


10 

the plaster or beams, to which the lines are attached 
“tie wires” (short pieces of wire which are passed 
Dimd the knob and twisted about the wire to be sup- 
rted in the manner used on overhead lines). The 
lobs hold the circuit wires from touching the wood or 
iier material over which they pass, and afford really 
jite good insulation in unfavorable places. So far I 
ye spoken especially of wiring which is in sight — run 
ing walls or ceilings — and have not referred to concealed 
ping, which, however, is even more often met with ; in- 
led, is almost always found in dwellings and fine build- 
£s of all kinds. Concealed wiring, if done at that stage 
, the construction of a building just before the lathing 
jbegun, is not difficult, as the spaces between the floors 
d walls are easily gotten at, and the wires may be 
tated or tacked to the timbers without trouble and 
pught out wherever wanted, the chief precaution being 
place them where they will be least likely to be dis- 
rbed in any way by the workman in putting down floors 
i lathing; but to successfully conceal the wiring in a 
ilding already finished, without taking up the floors 
jvery objectional proceeding), is a rather troublesome 
^tter. Each wire has to be pushed through a small 
inlet-hole into the space between the floor or walls, and 
^n worked about until it can be caught and “fished 
jt” through another small hole at the point wheTe it is 
mted. Sometimes it takes a great deal of time and 
tience to do this, and when done there is always an 
certainty as to whether the wire lies where it will give 
od service. 

It is plain that in this matter of concealed wiring the 
>advantage is that one cannot get at it easily to locate 
d remedy troubles, and this has caused the extensive 
e of the conthiit system. This excellent system consists 


20 


ELECTRICITY FOR ENGINEERS. 


of tubes made of water and fire proof insulating materia 
which are placed in the building before the lathing an 
flooring has been done ; they are fixed to the timbers, an 
are run wherever circuits are called for. It is so arrange 
that wires may be drawn into these tubes, and it is thus 
very easy matter to replace one at any time in case'] 
causes trouble. In many of the finest modern building 
all wires, for whatever purpose, are placed in these cor 
duits, the slight likelihood of troubles occurring, and th 
ease of making repairs in case they do, more than makin 
up for the increased cost. 

The course which a current should take to reach an 
desired point ought to be carefully planned out before an 
work is done upon it. The wires, if exposed, should ru 
where they are least likely to be interfered with in any waj 
lest they should be loosened, broken, or stripped of the: 
insulation; for instance, they should be fastened flat t 
beams or ceilings, rather than pass from beam to bear 
through the air, and should be entirely out of ordinar 
reach. They should avoid as much as possible dam 
rooms, and, whether concealed or exposed, should kee 
carefully away from pipes of all kinds, and from othe 
wires, to avoid the chances of accidental connections ; an 
last, but not least, other things being equal, the shortes 
wav is the'best, as less wire is needed and less resistanc 
added to the circuit. 

This is all I shall say concerning “ light current” cii 
cuits in general. More, however, will be said of ther 
when speaking of the special “ light current ” applications 
and I will now go on to a brief statement of some point 
relative to electric bells. 


LIGHT CURRENT WORKING. 


21 


ELECTRIC BELLS. 

Of all electrical devices the vibrating electric bell is, 
believe, the most familiar, and certainly is one of the 
iost useful. So familiar is it, indeed, that a description 
I almost unnecessary. I will ex- 
lain it briefly, however, by refer- 
kce to Fig. 1 , in which M is the 
[ectromagnet, and A its soft iron 
■mature which it is capable of 
jitracting (p. 3). 

The armature is provided with a 
ammer, H, and is supported by 
jie spring, S, which always keeps it 
ressed back lightly against another 
iring, P, thus holding the ham- 
ler a short distance away from 
le gong, G. The circuit enters 
t the binding-post, B, passes 
irough the coils of the electro- 
lagnet, then to the spring, S, 
p the armature, thence to the platinum-tipped spring, P , 
rid passes out at binding-post, B. 

Now, when the two binding-posts are connected with a 
attery, the electromagnet attracts its armature, causing 
le hammer to strike the gong a blow, and at the same 
me causing the armature and the spring, P, to part, thus 
reaking the circuit. As soon as the circuit is broken the 
lagnet loses its power, and the armature returns to its 
riginal position, closing the circuit again. This action is 
ept up as long as the battery is applied, the bell giving 
continuous ring. 

In choosing electric bells, one will find it of advantage 



Fig 1. 




















‘22 ELECTRICITY FOR ENGINEERS. 

to use those which have covers fitting as tightly as possi 
ble, in order to prevent the entrance of dust or insects! 
and to employ only those which have all their parts fas' 
tened to an iron frame, so that they may be kept in the 
same position relatively to each other. 

If the parts are fastened to a wooden back, there li 
likely to be trouble from the warping due to dampness 
The points which make contact between the armature anc 
spring should be of genuine platinum to insure a gooc 
connection, as it is much less likely than any other meta 
to become dirty or corroded. It is important in all bells 
to have an arrangement for changing the position of th( 
spring upon which the armature is carried, so that tht 
armature will rest nearer or farther from the magnet; anc 
it is also important to have a screw (represented at J ir 
the figure) to move the spring, /*, to or from the magnet 

PUSH-BUTTONS. 

Besides the bell itself, ‘the push-button is perhaps the 
next important part of a bell circuit. It is, of course, th< 
part at which the circuit is closed and the bell causec 
to ring. The most common form of push-button is mereh 
a round piece of wood or hard rubber, having two thir 
brass pieces fastened to it by two of their ends, the othe; 
two ends overlapping but not touching. They are mad< 
to touch by pressing upon a small knob. The circuit wire: 
are each fastened to one of the brass strips, and a tigh 
cover screws down over them. Push-buttons are made o 
a great variety of forms and materials; most often the] 
are intended to be screwed to walls, but sometimes to b< 
attached to flexible conductors for convenience in movin< 
them about. The principle of them all is the same, — th< 
closing of the circuit by the bringing together of two con 


ELECTRIC BELL CIRCUITS. 


23 


act springs by pressure. The best push-buttons are 
hose in which the contact pieces are quite springy, so 
hat a slightly rubbing contact is the result when they are 
Drought together, which keeps the connecting surfaces 
pnght, and makes the closing of the circuit more certain. 
Buttons in which the contact pieces are unyielding are 
|nuch less sure, as the contact surfaces tend to become 
dirty. All buttons, but especially those intended for out¬ 
door use, are much better when made with hard rubber 
backs and bronze covers than when made of wood, as 
-he wood is likely to warp and crack by the action of the 
leather, allowing dampness to enter which corrodes the 
contacts. The screws which serve -to attach the circuit 
jvires to the contact pieces should be of good size, so that 
*hey will bear being set up tightly, thus making sure of 
good contacts. 


ELECTRIC BELL CIRCUITS. 


The circuit for ringing a single electric bell from a 
ingle point is of the simplest description. Fig. 2. 

& G, 



Fig, 2. 


Starting at P, Fig. 2, one of the springs of the press- 
iutton, the circuit passes to B', one of the battery termi- 
lals, through the battery, out at B, thence to the bell 
erminal G, out at G', and then passes to the other contact 











24 


ELECTRICITY FOR ENGINEERS. 


spring, P', of the press-button. The circuit is thus closed 
except at the button between P' and P, and a closure 
here will immediately set the bell ringing. 

The arrangement for ringing more than one bell from 
the same point is represented by Fig. 3, and will explairj 
itself. One should never try to ring several bells from 
the same button by connecting the bells in series ; that 
is, arranging them as one would several cells to form a 
battery, for in this case, the bells being in the saftid 
circuit, and having the same current passing through 
them all, trouble would be caused by the fact that each 
bell would break the circuit for all the others, producing 



Fig. 3. 

very irregular and uncertain ringing. For ringing the 
same bell from several stations the connections are as fol¬ 
lows : — (Fig. 4) where C is the battery, B the bell whicf 
is to be rung from a number of different points, P 1 , P 2 , and 
P s push-buttons located at various places, and A 1 , A 2 , anc 
A z annunciator drops placed near the bell to show whicE 
of the buttons causes the bell to ring. These annunciatoi 
drops are necessary when a great many buttons are con¬ 
nected to one bell, as is the case in hotels, etc., but maj 
be dispensed with when the number of buttons is small 
The kind most frequently met with is the “ Gravity 
Drop,” which consists of a small electromagnet placed ir 


























electric bell circuits. 


25 


.he circuit of the button from which it is intended to be 
operated. This magnet has an armature which normally 
lolds up and out of view a small tablet, upon which is 
;he number or name corresponding to the button. When, 
lowever, the circuit is closed at the button, the armature 
)f the magnet is attracted, allowing the tablet to fall into 
dew; at the same time the bell rings, and it is at once 
mown that a call has come from a certain definite point. 

A large number of these drops placed in an ornamental 
fame and surmounted by a bell are found in almost every 
lotel and public building. The annunciators of different 



mnufacturers differ so much in the details of their con¬ 
traction that it is difficult to give any general instructions 
oncerning them. The main point, however, is to keep 
le drops in correct adjustment, so that they will be sure 
> fall when they should, but not to fall from any acci- 
ental jar or vibration to which they may be subjected. 

What every one wishes to know is what to do to a bell 
hen it will not ring. First take a look at the battery 
nd see whether it has been run down or not (p. 11). 

as will probably be the case, it has not, and is still in 
ood condition, one should examine the circuits carefully 















26 


ELECTRICITY FOR ENGINEERS. 


throughout, looking for a broken wire, one cut off by 
a too-firmly driven staple, or one eaten off by moistur^ 
or a chance drop of sal-ammoniac. The firmness and 
cleanness of the contacts at the binding-posts of the 
battery and bell and at the screw connections of the] 
button should be looked to, and the contact points in] 
the button, and the contacts between armature and spring] 
in the bell, made bright, if need be, by the use of a thin 
flat file. One should be on a watch for a contact between] 
the two wires of the circuit between the battery and bell, I 
as this would prevent the bell from ringing by stealing) 
the current away from it when the button was pressed.] 
The trouble is most frequently in the adjustment of the] 
parts of the bell, and it becomes necessary to readjust 
them, which may be done in most bells in some such way s 
as this : — 

By bending the hammer or moving the magnets, arrange] 
matters so that the gong will receive a blow just as the! 
armature is about to strike the ends of the magnet; then,; 
by moving the screw generally provided for the purpose,] 
adjust the armature so that it naturally rests so as to hold) 
the hammer perhaps i inch from the gong. Now adjust! 
the contact spring, by its screw, so that it will follow thej 
action of the armature through a part of its stroke; see i 
that everything is clean and tight, and your bell ought to; 
ring. Of course bells vary so much in their construction! 
that directions cannot be given which always apply. 

If, instead of finding the battery all right, it is found to; 
have been exhausted, it is probably due to there having;! 
been a permanent closing of the circuit, not complete,; 
enough perhaps to keep the bell ringing, as this would bejj 
immediately noticed, but sufficient to injure the battery.; 
A double-pointed tack driven tightly over both wires may 1 
be to blame; the Insulation of the wires may have been! 


BURGLAR AND FIRE ALARMS. 


27 


worn off over a pipe, or any such accident may have hap¬ 
pened. The permanent closing at the button by the 
sticking together of the contact springs may take place, 
but it is detected by the continuous ringing of the bell 
before the battery has been harmed. 

It is best to see that bells are put up with the gong 
down, as they work much better in this position than 
when the box is below; and it is worth while to plan with 
pome care their locations, so that they will be heard dis¬ 
tinctly where it is desired they should be, but not disturb 
those not concerned with them. 

The use of bells of different tones, of the cow-bell and 
sleigh-bell shapes and the “ buzzer ” form, is of advantage 
where many are used, as it prevents much confusion. 


BURGLAR AND FIRE ALARMS. 

Most of the Burglar Alarm and Automatic Fire Alarm 
systems consist of the electric bell and annunciator sys- 
em applied to these special purposes, and having the 
dosing of the circuit accomplished automatically instead 
>f by means of the common press-button, 
i The ordinary burglar alarm makes use of circuit closing 
levices which act when any attempt is made to open the 
loors or windows. The closing of the circuit rings a bell, 
>f course, and locates the point where the entrance is be- 
ng made by throwing the appropriate annunciator drop. 

In the automatic fire alarm system the circuit is closed 
vhen the temperature of any part of the building to be 
>rotected rises above a certain dangerous point, 120° F. 
>r so. The melting of a fusible metal may be made use 
>f to allow two contact springs to come together, which 




28 


ELECTRICITY FOR ENGINEERS. 


it ordinarily holds apart, or the circuit may be completed 
by the expansion of metals or liquids which force metallid 
connections together when a certain degree of heat is 
reached. If a building is thoroughly equipped with these 
arrangements for automatically sending in an alarm of firel 
it is really a great safeguard. 

To these two applications of electricity most of the re>| 
marks concerning electric bell work apply; but one should 
not fail to make frequent tests of the arrangements by] 
actually operating them as they would be operated in prac-1 
tice, to be sure that they would work properly in case the! 
occasion for their action should arise. 


ELECTRIC GAS-LIGHTING. 

I come now to speak rather briefly of the very impor-J 
tant application of electricity to the lighting of gas, which] 
has become a necessity in almost all dwellings of any pre4 
tentions as well as in office buildings and other public 
places. Besides being a great convenience, it does awayj 
with the use of matches, and largely reduces the fire risk. 
Gas is lighted electrically by three different methods a 
the Pendent System, Automatic System, and the Multiple 
System. 

The Pendent system is by far the most frequently used,; 
and is so called from the fact that the gas is lighted byj 
pulling a pendent chain connected with the burner. The 
arrangements for pendent gas lighting are very simple. 

A battery (B) of five or six Leclanch6 cells is required j, 
one pole of which, R , is connected to the main gas-pipei 
by a soldered contact; the other pole is connected to theii 
spark coil, S, and from this a wire leads to the distribii 







ELECTRIC GAS LIGHTING. 


29 


itins: board, D, from which wires branch off to the 

o 77 

various burners, one of which is represented at G. 

Each wire going to the burner is connected to a small 
:ollar placed around the gas-tip and which is insulated 



M 

Fig. 5. 


from the fixture by asbestos. Each collar has a little wire 
contact point placed close to the gas-slit, at which the 
igniting spark is produced. It is plain from the figure that 
it is only necessary to connect the insulated collar of a 
burner with some part in contact with the fixture in order 



























30 


ELECTRICITY FOR ENGINEERS. 


to close the circuit through battery, spark coil, wiring, and 


Piping. 

The “spark coil” is simply an electromagnet wound 


with a few turns of large insulated wire and with its core 


made of a bundle of fine soft iron wires. The closing of 
the circuit through it of course magnetizes it to a highs 
degree, and the breaking of the circuit at the burner con-; 
tacts causes the spark that does the lighting of the gas by 
discharging its magnetism. 


The pendent burner is a burner having pivoted to it an 
arm which is worked by the chain. This arm carries a 
spring wire, which makes contact with the wire upon the 
insulated collar when the chain is pulled, and then snaps 
off again, making and then breaking the circuit, charging 
and discharging the spark coil, and producing a spark in 
line with the gas-slit. There is a spring which acts 
against the pull upon the chain, keeping the contacts nor¬ 
mally separated. A pawl on the arm advances by one 
tooth, at each pull of the chain, an eight-tooth ratchet 
wheel which carries the four-way gas-cock, so that gas is j 
alternately turned on and off the burner. 

Sometimes the burners are made so that the pulling of ; 
the chain simply makes the spark, thus requiring the gas i 
to be turned on in the ordinary way. 

Ordinarily the pendent system works very well, giving 
very little annoyance and proving a gre^t convenience, but 
there are certain points which sometimes give trouble. I 
Owing to the necessity of using an open circuit battery for 
this work, so that the attention required shall be almost ; 
nothing, a permanent accidental closing of the circuit is I 
especially to be avoided, as it means the ruin of the battery j 
and the annoyance of having the gas-lighting system useless 
until the battery can be replaced. It is a great nuisance I 
fo have to descend to the use of matches throughout a 







ELECTRIC GAS LIGHTING. 


31 


juilding when the gas for any reason fails to light electri- 
illy. There are devices on the market, however, which 
utomatically open the circuit and protect the battery upon 
le formation of a permanent closed circuit, and one of 
lese should be used on all gas-lighting systems. 

> It is the sticking together of the contact points of the 
jurners that is the most frequent cause of a permanent 
losed circuit; and one should examine each burner to 
lake sure that this cannot happen, bending the moving 
bring wire contact, if need be, so that there is no possi¬ 
bility of its catching upon the contact on the collar. 

The wires running along the fixtures to the burners 
ometimes accidentally become connected to the piping, 
>y rubbihg upon some sharp part, which wears away their 
nsulation, and produces the same trouble. This is espe- 
lially likely to be the case where the wires run inside the 
rasing of the fixtures, unless the best of wire is used, hav- 
ng as an extra insulation a very small rubber tube slipped 
&ver its whole length. 

The best fixture wires have several distinct coverings of 
:otton and an inner winding of silk, and are of colors to 
natch different colored fixtures. 

It is best, however, to avoid the ones covered with me- 
allic bronzing, as it may cause “ leaks.” 

At the point where the wire goes up to the burner, it is 
veil to slip over it a short piece of glass tubing, as with¬ 
out this precaution the insulation sometimes takes fire, 
turning down to the fixture and forming a contact between 
the wire and pipe, with the usual effect of permanently 
closing the circuit. 

Joints in movable wall brackets are frequently the cause 
of wearing through of the insulation of the wire, unless 
sufficient slack is left at these points; and the rosettes 
through which the wires have to pass in coming out of 
the walls to the fixtures sometimes cut the covering. 



32 


ELECTRICITY FOR ENGINEERS. 


It is, of course, more important in gas lighting than in 
any other light current work to keep as far as possible] 
away from all pipes, or other metallic connections taj 
ground ; and in all parts of the circuit, where practicable] 
concealed work should be done with this fact in mind. 

One should see that a separate wire is run from the disl 
tributing board to each chandelier and to each group of three 
or four brackets. It is easy then to locate and disconnect 
any wires upon which trouble occurs, without affecting 
the others. It is too often the case, however, that this 
matter is slighted, and only a few wires run for a largd 
number of burners, a great many branches to various points 
being taken off the same wire, often at places between 
floors or in walls which it is extremely difficult to reach.! 

If any trouble occurs anywhere in a building wired in 
this way, it is likely that a large part of the burners will 
have fo be thrown out of use. 

In testing to find upon which of the wires leading from 
the distributing board the permanent closed circuit is 
located, it is best to disconnect all the wires, and then, 
supposing the battery to be of its usual strength, to touch; 
the wires one by one to the distributing strip, the one 
which gives a spark being the defective one. 

This should, of course, not be connected again until 
the trouble has been remedied. 

If it is found that certain burners fail to give a propel] 
spark when operated, it may be because the contact points] 
have become corroded, or covered with soot from tha 
flame; they should be cleaned with a small file and the 
collar rotated a little so that the point will not be exactly 
in line with the gas-slit. 

Incandescent lights are now being very largely applied 
to gas fixtures, and gas-tight insulating couplings are used 
to disconnect the fixtures electrically from the piping]; 



ELECTRIC GAS LIGHTING. 


oo 


in accordance with the Underwriters’ Rules, making it 
impossible to use the ordinary form of gas-lighting cir¬ 
cuit wh::h utilizes the pipe as the return to the battery. 
It is necessary, therefore, to disconnect the pole of the 
gas-lighting battery from the gas-pipe, and to run instead 
wires from it to the various fixtures. 

Under no circumstances should the insulating coup¬ 
lings, which the electric lights demand, be bridged over 
j by wire in order to make the gas lighting work in its 
usual form, as this thwarts the purpose for which the 
couplings were used, and creates a certain amount of dan¬ 
ger from fire. Indeed, electric gas lighting had better not be 
(used on fixtures to which incandescent lights are attached. 

The automatic system is used for lighting and extin¬ 
guishing burners that are out of reach or at a distance. 
The arrangement is as follows: (Fig. 5 ), in which A is 
the automatic burner, and K the key which controls it. 
From the distributing board, D , is run a wire to one con¬ 
tact point, Z,, of the key, K. From the two contact points, 
M and N, wires are run to the burner, the wire from M 
going through the small electromagnet, O, which is ar- 
ranged to turn on the gas through the vibrating contact, 
Q, which is placed close to the gas-slit, and at which the 
spark is produced, and thence to the fixture. The wire 
from N passes through an electromagnet, P, arranged to 
turn off the gas, and thence to the fixture. The contact 
M is forced against the contact L when the white button 
of the key is pressed, operating magnet O and vibrator 
Q , and turning on and lighting the gas. When the black 
button is pressed, contacts ,.V and L are forced together, 
operating the magnet P, and shutting off the gas. 

The same automatic burner may be operated from more 
than one point by adding several keys, the contacts of 
which are connected with the wires from the correspond¬ 
ing points of key, W, by branch wires, 




34 ELECTRICITY FOR ENGINEERS. 

It is better to place an automatic burner where its light 
can be seen from the keys which are to operate it, asj 
sometimes, when not working properly, the burner may 
turn on the gas without lighting it, allowing it to escape 
without immediate detection if the burner’s light is invis-^ 
ible from the key. 

Automatic burners are especially useful for lighting 
and extinguishing the gas at the foot of a flight of stairs 
from the floor above, or the opposite; but their general 
use is not so satisfactory as that of pendent burners, asj 
they are expensive and more likely to get out of order.1 
The multiple system of gas lighting is largely used.; 
to light a number of burners simultaneously in halls,: 
churches, or other large buildings. The burners for this 
system are made with highly insulated porcelain collars, 
each burner being provided with two contact points se-l 
cured to the porcelain, one on either side of the gas-slit 
and separated from one another a small fraction of an! 
inch. The source of the electricity for doing the lighting] 
is a small “static” machine operated by hand, and pro-] 
ducing sparks similar to the ones seen to jump fro ml 
moving belts. The burners are connected together in 
“ series ” by bare copper wires run upon porcelain knobs! 
to secure good insulation. The current, in order to tra- 
verse the whole circuit, has in turn to jump across the gas-] 
slit of each burner. When the lighting is to be done the] 
gas is turned on and the machine connected to the cir-1 
cuit; the spark produced at each burner ignites the gas.] 
In damp weather it is not always easy to secure a good^ 
spark, as the machine is not likely to work especially well. 
The discharge of the machine, too, will sometimes leak 
around a burner, instead of sparking across between its: 
contacts, when the insulation is defective from dampness' 
or other cause, 





HEAVY CURRENT WORKING. 


35 




PART II. 

HEAVY CURRENT WORKING. 

j 

i By “heavy current 11 applications of electricity is here 
(meant the uses of the electric current for lighting as a 
(motive power, and for any other purpose requiring 
ja large quantity of energy in the form of electricity. 
Absolutely essential to these applications is the dynamo 
machine as a cheap and convenient means of generating 
jthe requisite current; indeed, without it, or something 
else equally good, the “ heavy current 11 applications would 
be impossible, owing to the impracticability and great 
expense of using a battery to furnish the current. 

It must be remembered that energy or power exists 
about us in various forms: in heat, in the motion of 
bodies, in chemical action, and electricity. Energy can 
never be created, nor can it be destroyed ; it can only be 
changed from one of its forms to another. When a cer¬ 
tain amount of energy is furnished to a machine, we can 
never receive back from the machine, in another form, 
any more energy than was given it. When the motion of 
a body of water is made use of to drive a water wheel that 
furnishes power to run a dynamo, or when the chemical 
energy in coal is changed into heat under a steam boiler, 
an engine operated by the steam, and a dynamo operated 
by the engine, we have good examples of the changing 
of energy from one form to another. 

In usings the battery to furnish electrical energy, zinc 
and other chemicals are consumed; while in running the 



36 


ELECTRICITY FOR ENGINEERS. 


dynamo, coal or other fuel is the material employed. In] 
both cases energy in the chemical form is changed intoj 
energy in the electrical form ; but the fact that many timesl 
as much electrical energy can be obtained from one dol] 
lar’s worth of coal by the use of the dynamo, as by one! 
dollar’s worth of zinc used in the battery, makes the] 
dynamo the practical method as regards expense, and! 
renders the use of the battery out of the question. Be-i 
sides, a battery requires a great deal of attention, occuJ 
pies a great deal more space than does a dynamo of the! 
same power, is very uncertain in operation, produces dan-I 
gerous fumes, and is generally unsatisfactory. 


THE DYNAMO. 

The principle which underlies the operation of the] 
dynamo is as follows:—An electromotive force (p. 4 )] 
is produced in a conductor (p. 3 ), which is made tea 
move through a region in which magnetic force is acting! 
Such a region is called a magnetic field, and an example] 
of one is the space between the two poles or ends of a] 
common “ horse-shoe ” magnet. The magnetic force in] 
such a case may be mentally pictured by drawing a num! 
ber of imaginary lines from pole to pole. It is along! 
these lines that the magnetic force acts, and they aid] 
called lines of magnetic force. It is only when the coni 
ductor is so moved as to “cut” through these lines of] 
force that an electromotive force is produced in it, no] 
electromotive force being produced if the conductor is] 
moved parallel to the lines . 1 Of course, if the electro! 

1 The amount of the electromotive force generated is greater as thel 
strength of the magnetic field and the rapidity of motion of the conductol 
are greater. 




THE DYNAMO. 


37 


motive force produced is allowed to act in a closed circuit 
(p. 3)^ a current will flow. 

In a practical dynamo of the simplest form a large horse¬ 
shoe magnet is used to furnish the magnetic field, the lines 
of force of which pass from pole to pole. Such magnets 
I are called field magnets, and they are always electro- 
I magnets (p. 3). Between the poles of the field magnet, 
|| mounted on a suitable shaft and bearings, is the arma- 
S ture which carries the conductors that “cut” the lines 
I of force, and in which the electromotive force is set up. 
I It is to the pulley upon the shaft of the armature that the 

I power is applied to rotate it . The armature is generally a 
cylinder built up of sheet iron with its shaft at right angles 
to a line joining the field magnet poles. It is built of iron 
in order to strengthen the magnetic field, as the magnetic 
force acts much more powerfully through iron than through 
air, or anything else. Upon the surface of this iron cylin¬ 
der are placed the insulated copper wire conductors in 
which the electromotive force is to be generated. They 
envelop the armature in various ways; but there are two 
general methods, to be described later. In an ordinary 
dynamo the electromotive force which the various conduc¬ 
tors generate are added together in various ways, but in 
the simple machine now being described the electromotive 
force which it produces is that obtained by adding together 
the electromotive force produced by one half the conduc¬ 
tors. The electromotive force generated is really alternat¬ 
ing, being in one direction in any conductor for one half a 
revolution and in the opposite direction for the other half; 
but while the current due to such alternating electromotive 
forces is very useful, it is not entirely suitable for power 
transmission and some kinds of lighting. For these pur¬ 
poses the current is required to be continuous ; that is, to 
flow in the same direction at all times, as does a battery 





38 


ELECTRICITY FOR ENGINEERS. 


current. In order to change the alternating current, which 
the dynamo naturally gives, into a continuous current, a 
commutator is used, which is simply an arrangement for 
automatically reversing the connection of each armature 
conductor to the circuit, just at the instant that the elec¬ 
tromotive force due to it is reversing its direction. In 
this way a current of a constant direction is obtained. 
This commutator is built up of parallel copper bars, suit¬ 
ably connected to the armature conductors, insulated from 
one another and grouped into a cylinder which is carried 
on the shaft along with the armature. The stationary 
copper or carbon strips which bear upon the commutator 
at opposite points are the brushes which carry away the 
current to the external circuit. 


DESCRIPTION OF PARTS. 

The field magnet of the dynamo is, as has already been! 
stated, an electromagnet, and is accordingly surrounded ; 
with one or more coils of copper wire, generally furnished ' 
with current from the machine itself. The portions of the j 
field magnet where the magnetic lines pass from it into ] 
the armature are called poles. The number of poles in j 
most continuous current machines is two, but in large j 
machines intended to run at a slow speed, four, six, j 
eight, and ten, and more poles, are sometimes employed. ; 
These machines are called multipolars, and usually require j 
as many field coils, or spools, as there are poles. The in-1 
tention in the design of field magnets is to cause as many I 
lines of forge as possible to pass through the armature, j 



PARTS' OF THE DYNAMO. 


39 


vith as small expenditure of electrical energy in the field 
:oils as possible, and to accomplish this without making 
[he magnets too large, heavy, or expensive, or without 

( finding on too much expensive copper wire to form the 
pools. The magnets of goo 4 machines are therefore of 
the best quality of wrought iron of liberal cross section, 
pd of compact form, so as to offer as little resistance as 
possible to the passage of the 
hagnetic lines, and hence re¬ 
quire less electrical energy to 
be expended in the spools. 

^or the same reason the 
tlearance between the arma¬ 
ture and the poles is made as 
bnall as possible. The field 
spools are preferably made 
;o surround the limbs of the 
nagnet near the armature, 
pd are excited or furnished 
[vith current in three princi¬ 
pal ways. ( 1 ) Shunt excita¬ 
tion (Fig. 8) is produced by 
jassing the current from 
>ne brush through the field 
ipoolssuccessively connected 
n series to the other brush. 

The spools thus receive the 
vhole electromotive force 
)f the machine, but their 
combined resistance is such that they only receive a 
/ery small fraction of the total current of the machine. 
This method of excitation is used on the great majority 
)f continuous current incandescent light machines and 
some power generators. Such machines are called shunt 

























40 


ELECTRICITY FOR ENGINEERS. 


machines. (2) Series excitation (Fig. 9) is effected by 
connecting the field spools in series with the armature, 
thus allowing the whole current which the machine gen¬ 
erates to pass through them. They are generally of sq 
few turns of such coarse wire that their resistance is so 



Fig. 9. 


Fig. 70. 


low as to reduce the voltage which the machine furnishes 
to the circuit but very little. Arc machines are almost all 
ways excited in this way, as well as street railway motors! 
etc. They are called series machines. (3) Compounj 
excitation (Fig. 10) consists of a combination of shunt andj 








































PARTS OF THE DYNAMO. 


41 


jjeries excitations — the spools being not only provided 
Ivith a fine wire winding of many turns through which a 
mall current circulates, but also with a coarse winding of 
1 few turns through which the whole current of the machine 
>asses. Street railway generators and alternating current 
dynamos are generally compound excited. 

The regulation of a machine to give the electromotive 
orce required is generally effected by regulating the cur- 
ent in the spools, thus changing the effect of the field 
nagnets. The e.m.f. produced increases as the current 
n the spools increases, owing to the increased strength 
)f the magnet, and vice versa. 

3 The armature core is generally built of a large number 
If thin circular discs of very soft sheet iro/i threaded on 
o the shaft and pressed together by lock nuts; a smooth 
veil-balanced cylinder is thus formed, capable of running 
:lose to the field magnet poles with safety. The necessity 
>f building up the cylinder of thin discs, instead of making 
t solid, will be explained when the “ losses ” in dynamos 
ire spoken of. Instead of a solid cylindrical form, some 
rores are composed of ring-shaped stampings clamped 
ogether and held upon the shaft by suitable metallic 
‘spiders.” This is the ring, or Gramme armature, and 
;>f course necessitates a different method of applying the 
:onductors from the cylindrical or drum construction, 
rhe necessity of having a core well balanced and firmly 
fixed to the shaft, considering the high speed at which it 
s to run and the large amount of power it is to absorb, is 
very clear. Frequently cores of both the cylindrical and 
ring form are toothed; that is, are built up of stampings 
having much the same appearance as gear wheels. When 
put together, the spaces between the teeth furnish slots 
for the windings, grooves on the surface of the core par¬ 
allel to the shaft. 






42 


ELECTRICITY FOR ENGINEERS. 


In winding continuous current armatures with the con¬ 
ductors in which the e.m.f. 
is to be set up, two general 
methods are followed, ac¬ 
cording as the core is of the 
cylindrical or ring form. In 
ordinary two-pole cylindrical 
armatures (Fig. 6) each turn 
of wire wound lengthwise of 
Fi 9- 6 ■ the core envelops nearly the 

whole of the iron, while in the ring armature (Fig. 7) 
the wire is threaded through and through the ring, each 
turn enveloping one half the total cross section of the 
iron. In both cases the winding in practice covers evenly 
the whole armature surface, and is divided into a great 



many separate coils, suitably connected to the commu¬ 
tator. Armatures for multipolar machines differ in the 
manner of making the commutator connections. Full de¬ 
scriptions of all kinds of armature windings and, indeed, 
concerning any feature of the dynamo, may be found in 












PARTS OF THE DYNAMO. 


43 


| P. Thompson’s “ Dynamo Electric Machinery.” The 
Isulation of the armature conductors from one another 
ijid from the core is perhaps the most vital point in 
|mamo construction. If this is not carefully attended to, 
jte armature is very likely to be ruined by short-circuiting, 

■ the useless and dangerous flowing about of the cur- 
nt in the armature coils instead of it following the 
[eternal circuit. The iron core should be very carefully 
pvered with paper and cloth covered with shellac, and 
pe coils, wherever they overlie one another, should be 
jparated by shellacked cloth or paper. Mica is good for 
jch insulation. 

Cylinder and ring armatures with smooth cores, that 
not of the toothed variety, have to be provided with 
ands of German silver wire wound tightly over the sur- 
ice, in the plane of rotation, and carefully insulated from 
le winding, for the purpose of holding the armature con- 
uctors in place. For large armatures running at high 
peeds these bands have to be very carefully proportioned 
) withstand the severe pull upon the conductors by the 
lagnets and the strong tendency of the conductors to 
iy outward. An armature ought never to be allowed to 
an at a speed much higher than that for which it is 
itended. 

The commutator of the dynamo is a device, as already 
tated, for the purpose of obtaining a continuous or direct 
urrent from e.m.f.’s which, in any individual coil, are of 
n alternating character — reversing direction every half 
evolution. By means of it the connection of any coil to 
he circuit through the brush is reversed just at the in- 
tant when the direction of the e.m.f. in it is reversing, 
n connecting the coils of an ordinary two-pole machine, 
he last end of one coil is connected to the first end of the 
lext by attaching both wires to the same commutator bar, 






44 


ELECTRICITY FOR ENGINEERS. 


the last end of this coil is connected to the first end of a 
third coil by attaching both to the next commutator bar, 
and so on around the whole armature, there being as many 
commutator bars as there are coils. This will be made 
clear upon reference to Figs. 6 and 7. In multipolai 
machines the method of connecting coils to the commu¬ 
tator is the same as in a two-pole machine, except that the 
coils occupying similar positions under alternate poles are 
connected together. Commutators should be of good 
length, of a perfectly smooth cylindrical surface, and the 
hard copper bars which compose them should be very 
carefully insulated from one another by mica, as well as 
from the shaft, upon which they should be firmly held. 
The commutator connections, or conductors which con¬ 
nect the armature coils to the commutator bars, should 
be carefully protected from being broken, and from acch 
dentally becoming connected together by the failure oi 
the insulation between them. 

Upon the commutator bear the brushes, two sets being 
used in ordinary two-pole machines, and indeed, in some 
multipolars, which more often, however, have as many 
sets as there are poles. The two sets are made to beat 
upon the rotating commutator of a two-pole machine al 
points diametrically opposite, and are carried in brush 
holders upon a yoke, by means of which they may be 
moved together around the commutator, always remaining 
opposite. The position of the brushes is a matter oJ 
extreme importance, and will be spoken of later. The 
material of the brushes of the majority of machines now¬ 
adays is carbon, although most arc machines and alter¬ 
nating current dynamos still use copper leaf, copper gauze, 
or copper wire brushes. The conductors leading froir 
the brush-holders to the circuit should be of especially 
flexible cable, so as not to be broken by the frequenl 
movement of the brush-holder voke. 


PARTS OF THE DYNAMO. 


45 


( Having thus briefly and incompletely stated the princi- 
les upon which the dynamo acts, and having defined 
nd slightly described its most important parts, it is 
ow necessary to touch upon a few points common to 
jhe operation of all dynamos. It has already been stated 
ihat the output of any continuous current dynamo, or its 
fate of furnishing electrical energy or power, is found 
by simply multiplying the current in amperes which it de¬ 
livers by the e.m.f. in volts, which it furnishes to the 
External circuit as measured across its terminals. This 
Result is the output in watts; the output in HP is ob- 
ained by dividing this by 746. The output in kilo-w T atts 
s a common method of rating dynamos, and is found 
>y dividing the output in watts by 1000. Now, for every 
nachine there is an output above which it is impossible 
o continuously operate it wflth safety. This is called the 
naximum safe output of the machine. This output is 
mown to have been reached when any part of the wire of 
.he machine becomes overheated, or when the machine 
begins to spark badly under the brushes, or when the belt, 
Droperly tightened, begins to slip on the pulley. If a 
nachine is run at an output above the maximum safe 
jutput, it is said to be overloaded and is likely to be dam- 
iged or even destroyed. Overloading should be carefully 
ivoided as much as possible, and the name plate of a 
nachine should be consulted in this regard. The greatest 
illowable voltage and current are usually stamped upon it. 
[n regard to the sparking under the brushes just referred 
o, and the causes which produce it, it may be well to say 
i few words here. The most common cause of sparking 
s the improper position of the brushes on the commuta¬ 
tor. It will be seen by consulting Figs. 6 and 7 that the 
crushes are so made that, in passing from bar to bar, 
2 ach one bridges two neighboring bars, leaving the coil 






46 


ELECTRICITY FOR ENGINEERS. 


whose ends are connected to these bars short-circuited 
by it for an instant. Now, of course, at the exact instant 
when the e.m.f. in a coil is reversing, there is realty 
no e.m.f. produced in it at all, and hence no current will 
flow through the brush as it short-circuits it. But, if the 
brush is in such position as to short-circuit the coil at any 
other than this exact instant, the e.m.f. which the coil is 
then producing will send through the end of the brush a 
very large current, which, when broken by the passing 
away of the brush, will cause a destructive spark. It is 
readily seen now why the connection of a coil to the cir¬ 
cuit is reversed by the brush at the exact instant spoken 
of, rather than at any other. It is furthermore true that 
this position of the brushes gives the highest e.m.f. of any 
in which they can be placed. Sometimes sparking is pro¬ 
duced by a rough commutator or loose brushes, the brushes 
actually jumping from the commutator surface and tending 
to break the main current. Sparking not only burns away 
the brushes and, far worse, roughens the expensive com¬ 
mutator, but wastes some electrical energy. If, with the 
greatest care, the brushes of a heavily loaded dynamo 
cannot be placed so as to prevent bad sparking, or if any 
part of the machine is more than 90° F. hotter than the 
air of the dynamo room, one may be pretty sure that it is 
overloaded, and the load upon it should be at once dimin¬ 
ished. A dynamo is properly regarded as only a machine 
for changing energy in the mechanical form, such as a 
steam engine or water wheel furnishes, into energy in the 
electrical form. Owing to the presence of certain actions, 
no dynamo can convert all the power it receives into elec¬ 
trical energy, part of the power being inevitably changed 
into heat, which manifests itself throughout the whoh 
machine. Of the mechanical energy delivered to the 
dynamo, that fraction which it converts into electrical en- 


PARTS OF THE DYNAMO. 


47 


I 'rgy for use in the external circuit is called its efficiency; 
nd the part of the energy which is changed into heat 
nd lost, as far as electrical uses are concerned, is called 
he “ losses.” As heat is produced in any conductor 
jvhich is traversed by a current (see p. 4 ) part of this 
bss takes place in heating the wire with which the field 
hagnet spools and the armature are wound. There is 
^eat produced, too, by the rapid reversal of the magnet¬ 
ism in the iron armature core as it revolves in the field; 
nd if it were not for the practice of building up the core 
>f thin sheets, there would be much more loss in it, due 
to currents unintentionally set up in the core itself, just as 
ihey are intentionally set up in the armature wires. The 
friction of the armature shaft in its bearings produces some 
ieat, and there are various other minor actions which cause 
iome loss. The smaller these losses are, the larger will be 
the fraction of the power of the engine left as useful electri- 
:al energy ; that is, the higher will be the efficiency, and in 
arge machines it may reach as high as 92^. A dynamo 
vhich runs hot, it is generally safe to say, is not of very 
ligh efficiency. The selection of a dynamo best suited 
or a certain purpose must be based upon its first cost, 
ts efficiency, the amount of floor space it requires, its 
veight, and the amount of attention and repairs it is likely 
o call for. A small, light, cheap dynamo is sure to be of 
■ather low efficiency, while a machine of high efficiency is 
generally much more large, heavy, and expensive. It may 
be stated generally that a dynamo which is to run almost 
continuously at nearly its maximum output should be of 
rather higher efficiency, and hence higher first cost, than a 
machine which is to be run only a small part of the time, 
mostly at a small output. The value of floor space should 
also be taken into account when considering this question. 
Many people, although they are aware that the dynamo is 





48 


ELECTRICITY FOR ENGINEERS. 


a machine which absorbs a very large amount of mechan¬ 
ical energy in proportion to its size, do not see exactly 
how this power is expended, or why a loaded dynamo 
“ turns hard.” This point is made clear when we remem¬ 
ber (p. 3 ) that a conductor, such as an armature wire 
carrying a current, has all the properties of a magnet, 
and that these “wire magnets ” are moved in the vicin¬ 
ity of the field magnet only by overcoming the magnetic 
attraction and repulsion between the wires and the mag¬ 
netic field. One may become familiar with these actions 
by experimenting with the attraction and repulsion of a 
couple of small horse-shoe magnets. 

Dynamos are divided into two classes according to the 
manner in which they supply their energy to the external 
circuit. 1. A constant potential dynamo is one which is 
arranged to furnish the same electromotive force to the 
circuit, no matter what the size of the current flowing in 
it may be. (See Ohm’s Law.) 2. A constant current 
dynamo is one which is arranged to maintain the same 
current in the external circuit, no matter how high an 
e.m.f. may be required to overcome its resistance suffi¬ 
ciently to do so. (See Ohm’s Law.) These two classes 
of machines differ in their methods of excitation and remi- 

o 

lation. Constant potential is secured by compound exci¬ 
tation or even very nearly by shunt excitation. Constanl 
current is usually attained by the use of series excitation 
and some mechanical regulating device. Constant poten¬ 
tial machines are employed in almost all incandescenl 
lighting and transmission of power work, while constanl 
current machines run nearly all the arc lamps. 

CARE OF THE DYNAMO. 

One of the most important points in the care of s 
dynamo, and, indeed, of all electrical machinery, is the 


CARE OF THE DYNAMO. 


49 


jelection of a suitable place for it. The only way to pre- 
ent deterioration of the insulation and the probable early 
pstruction of a dynamo armature is to exclude all damp- 
jess, and all dust and shavings, especially of iron or other 
petals. There should be no overhead water or steam 
ipes or automatic sprinklers near the dynamos, lest they 
flow water to drip upon them; and oil-cloth covers 
fiould be provided with which to cover the machines 
Ifhen not in use. These should not be put on when the 
lachine is very hot. The flooring of the dynamo room 
rould be very dry, and the wood thoroughly “filled” 
fith oil to exclude moisture. The building must be very 
Libstantial to withstand the weight and vibration of the 
eavy machines. If the dynamos are placed in the base- 
lent, which makes the providing of firm foundations for 
iem an easy matter, a good flooring of oil-filled plank 
iiould be put down over the cement or concrete. Deep 
rick piers are the only foundations good enough for 
eavy machines ; upon these are placed the wooden slid- 
ig bases upon which the machines are mounted. It is 
sry important to insulate in some degree the machines 
om the piers, by using dry oil-treated wood for the bases. 

The placing of the dynamos so as to economize floor 
)ace and yet not to so crowd them as to make the at- 
mdant’s duties dangerous, ought to be carefully con- 
dered. The possible addition of new dynamos should 
e provided for. Indeed, in this work one has to be con- 
antly thinking of the future, and ought to aim to do as 
pie work as possible which will soon require to be done 
|ver. The great majority of dynamos in use are driven 
jy belts from the engine pulleys or from pulleys upon a 
lain shaft, but many private dynamos are directly con- 
ected to the engine, the engine and dynamo being 
lounted upon the same base and having their shafts 



50 


ELECTRICITY FOR ENGINEERS. 


connected by a suitable coupling. This arrangement re¬ 
quires less room than a belted dynamo of the same out¬ 
put, as the space taken up by the belt is saved, and where 
floor space is limited this advantage may more than make 
up for the somewhat greater cost of the direct driven ar¬ 
rangement. The belts used for driving dynamos should 
be of the very best quality, and of ample size to transmit 
the greatest power that the dynamos are capable of safely 
receiving without undue slipping. The steadiness and 
promptness of the regulation of the engine are of the 
greatest importance, especially in incandescent lighting, 
although it is very essential in transmission of power work 
and even in arc lighting. A very slight irregularity in the 
dynamo speed can be noticed in incandescent lights — 
even so slight a one as that produced by a stiff lap in the 
driving belt, and any fault in the government of the engine 
is very noticeable. An engine ought to be able to in¬ 
stantly change from full to no load — a change taking 
place very often in electrical work — without showing any 
signs of “racing.” It is the lack of good regulation 
which has prevented water wheels from being used in a 
great many instances in which they might otherwise have 
been employed. The care of bearings is one of the mosl 
important points in dynamo tending, for the dynamo is a 
machine, the shutting down of which during working 
hours, means a great deal of annoyance and expense. II 
must be kept running at all hazards, and to do this hoi 
bearings must be prevented. With the modern self-oiling; 
bearings, in which a loose ring on the shaft continuall) 
carries oil from a reservoir over the bearing surface , 
almost no attention is required, except occasionally 7 t<^ 
fill up the oil reservoirs, draw off the old oil, and keefj 
grit and dust out of the bearings. Most modern dynamcj 
bearings are self aligning and self adjusting, so that heat 


CARE OF THE DYNAMO. 


51 


ing is now seldom produced by non-alignment or by caps 
too tightly screwed down. Ordinary bearings with sight 
feed oil cups are familiar to everyone | they only require a 
little care and watching to give good results. If a bear¬ 
ing does become hot, it is probably due to lack of oil, grit 
in the bearing, caps set down too tight, or poor alignment 
of the shaft with the bearing. 

Cold oil poured rapidly through the bearing will cool 
it gradually. Many engineers prefer to use heavy oil for 
this purpose. 

Before going on to the electrical points which bear upon 
the subject of the care of dynamos, it will be well to add 
a few words concerning the matter of personal safety in 
handling electrical machinery. The danger, which is 
greatly exaggerated by most people, is of three kinds : the 
Drdinary danger due to high speed belts and pulleys, 
ffectrical shocks, and electrical burns. Nothing need be 
said in regard to the former, except that sufficient space 
should be provided in the dynamo room so that the at- 
:endants may not be required to pass through dangerously 
:rowded spaces between belts or moving machinery ; that 
suitable guards should be provided for the belts, to catch 
;hem in case they accidentally come off the pulleys; and 
; hat all large high speed pulleys should be built with 
vooden rims to reduce the danger from bursting. 

The constant possibility of heavy momentary overloads, 
o which electrical machinery is especially subject, makes 
hese precautions very needful. In regard to electric 
hocks, it may be stated that even a momentary continu- 
)us current, received in the usual accidental manner, when 
)f a voltage much above six or seven hundred, may be 
langerous. Alternate current shocks are far more painful 
han those from continuous current, and probably a much 
ower voltage would be dangerous. Of course if a shock 



52 


ELECTRICITY FOR ENGINEERS. 


were received through a part of the skin that happened to 
be damp and more tender than that of the ordinary perr 
son’s hand, and if the shock were to continue for some 
time, a lower voltage than that named might be dangerous. 
All electric shocks are to be avoided, and the best way to 
do this is to observe the following rule. (1) Never touch 
with two parts of the body at the same time, any two parts 
of an electrical apparatus, except when it is certain that 
there is no electromotive force between the parts touched* 
(2) Never touch with any part of the body any portion of 
any electrical apparatus unless it is certain that the place 
upon which one is standing is dry, and more or less insu¬ 
lated from ground. A dry board can usually be found to 
stand upon. (3) Avoid touching any part of a circuit 
which is being broken. This is to avoid the high voltage 
produced by the ceasing of the current in electromagnets 
which may form part of the circuit. The first rule is of 
course a very obvious one. The second refers to the 
danger due to a grounded circuit, which is illustrated as 
follows : Suppose some point in a circuit to have become 
in some way connected to the ground ; and the dynamo 
attendant to be also grounded by either standing upon a 
damp floor, the ground, or by touching some grounded 
metallic body. Then when he touches the circuit any¬ 
where else than at the grounded point, he will receive a 
shock more or less severe according as he touches it al 
a point far from or near to the grounded portion. The 
current will divide at the point touched, most of it follow¬ 
ing the wire, but a little passing through the attendant’s 
body, through the earth, and back to the wire at the 
grounded point. This is a very common and very danger¬ 
ous way of receiving shocks. No circuit ought to bj| 
run when grounded—especially an arc circuit. Among 
extremely dangerous machines and circuits, employing 


CARE OF THE DYNAMO. 


53 


currents of from 1000 to 5000 volts, should be included 
(those for alternating current incandescent lighting and 
larc apparatus. By following the rule of keeping one hand 
jbehind the back or in the pocket when dealing with high 
(potential apparatus, by noticing where one is standing, 
land by using insulated screw-driver and pliers, shocks 
Imay generally be avoided. Electrical burns may ordi- 
inarily be avoided by never allowing any part of the body 
to be nearer than is absolutely necessary to the point 
(where a circuit is broken. It is the arc which follows 
upon breaking the current that does the burning. Its 
|heat and brilliancy seriously injure the eyes if they are 
too near it; and it is a good plan to face away when a 
circuit is being broken, as well as to wear heavy rubber 
gloves for the protection of the hands. 

Accidents will occur from electrical apparatus, but they 
are (more than accidents of almost any other kind) due 
to personal carelessness. 

By far the greater part of the care required by a direct 
current dynamo or motor has to be given to the commu¬ 
tator and brushes, in order to avoid sparking, heating 
of the commutator, and noise. The adoption of carbon 
in place of copper as the material of brushes has done a 
great deal, however, to reduce this. In the first place, 
the commutator must be in good condition: its surface 
must be perfectly cylindrical, and high or low bars must 
be remedied, as they will cause sparking. If there is any 
considerable irregularity in the commutator surface, the 
armature should be taken out of the machine, placed in 
a lathe, the commutator turned down to a true surface, 
and finished by the use of fine sandpaper, not emery 
cloth. If there are only slight irregularities in the com¬ 
mutator surface, coarse and then fine sandpaper held on 
a suitable block will remedy the trouble. All traces of 


54 


ELECTRICITY FOR ENGINEERS. 


copper chips and dust should be removed from the com¬ 
mutator and its connections before replacing the armature 
in the machine. It is never a good plan to use a file upon 
a commutator; it is far better to use sandpaper of differ¬ 
ent grades, finishing with a fine paper. Oil should not 
be allowed upon the commutator in any quantity, as it is 
likely to damage the insulation between bars. The com¬ 
mutators of machines using copper brushes may, however, 1 
be lubricated by applying a very thin coating of vaseline,? 
sufficient to stop the noise which the brushes make. If 
the brushes used are of carbon, a little oil may be applied 
to the commutator,.upon the end of the finger, to lessen 
friction and stop the chattering noise. People tend to 
lubricate commutators too much ; and it is well to be on 
one’s guard against doing so, or even attempting it at all' 
upon very high voltage machines. Good modern machines 
are furnished with brush-holders, which not only give 
excellent electrical connection to the brushes, but allow 
them to accommodate themselves to the surface of the 
commutator, and to “feed” as they wear out. The. 
holders are all mounted on a yoke by which they may all 
be rotated about the commutator, still keeping their proper 
relative positions. Carbon brushes are made either of the 1 
radial variety, bearing upon the commutator in the direc4 
tion of the radius, or of the tangential type, which bear j 
at an angle of 90° or less with the radial. Copper brushesl 
are almost always tangential. Radial carbon brushes arej 
beginning to be very largely used. They enable the 
armature to run in either direction without any change* 
being required,' and are easily made self-feeding and self-1 
adjusting so as to require almost no attention. Tangen- j 
tial brushes, bearing as they do upon the commutator, 
allow of only one direction of rotation of the armature, 1 ] 
and care must be taken not to run an armature “ against ‘ 


CARE OF THE DYNAMO. 


55 


he brushes.” When a machine is shut down, it is always 
est to remove the brushes from the commutator. Copper 
rushes may be made of either copper gauze, bunched 
ppper wires, or copper leaf. They cut the commutator 
:orse than carbon brushes, spark far worse, give rise to 
tore dangerous conducting dust, require frequent trim¬ 
ming and setting, and are not so readily made to take care 
f themselves for long periods of time. On the other 
and, they will carry off from the commutator, without 
ndue heating, a much heavier current than will carbon 
rushes of the same bearing surface. The fitting of 
arbon brushes to the surface of the commutator is easily 
bcomplished as follows: Place the brushes in the holders 
i their proper positions ; wrap the commutator with coarse 
Endpaper placed face up; then rotate the armature or the 
kndpaper wrapping by hand until the brushes bearing 
^on it have been worn down to a proper surface. An 
xcellent fit can very quickly be obtained in this way. 
topper brushes generally have to be filed in a vice until 
iie proper bevel is obtained, to give a good bearing upon 
ie commutator when they are properly placed in the 
olders. They should never be run in a ragged or frayed 
ondition. The pressure of brushes upon the commu- 
a,tor ought never to be heavy, and it should not be 
ttempted to make a badly fitted brush work properly by 
ncreasing its pressure, causing undue wear and heating. 
The brushes of two-pole machines should bear upon the 
:ommutator at exactly opposite points. These points can 
generally be found by counting the bars. In four-pole 
[nachines the brushes ought to be a quarter apart, and 
to on with the higher poled machines. Something has 
ilready .been said concerning the proper position of the 
crushes upon the commutator to give the least spark ; the 
pnly way of ascertaining their position is by trial, mov- 






56 


ELECTRICITY FOR ENGINEERS. 


ing the yoke which carries all the brushes until the mos 
satisfactory position is reached. In most machines, how 
ever, the brushes require a slight shifting when the loac 
changes, to keep down the spark. With carbon brushes 
this change is very slight. As has been remarked unde; 
the subject of “ output, 1 ’ the heating of a dynamo is a con 
sideration which, with sparking, limits the work it cas: 
safely do. It is always well to keep a sharp lookout foi 
overheating by occasionally feeling the field spools, anc 
holding one’s hand in the blast of hot air which comes 
from the revolving armature. When a machine is danger¬ 
ously overheating a smell of hot shellac may generally be 
noticed. If overheating takes place at a load less thar 
the one for which the machine is intended, one may be 
pretty sure something is wrong, very likely in the arma¬ 
ture. If it is ever necessary to run a machine at an over¬ 
load, one should be very watchful to detect the first signs f 
of overheating in time to prevent the destruction of the 
insulation by carbonizing it, and the consequent ruin o: 
the armature or field spools. It is certainly safe to sa) 
that as long as one can bear the hand continuously on the 
hottest portion of a dynamo, it is in no danger from over¬ 
heating. About the worst accident which can happen ic 
a dynamo is a short circuit. This generally comes aboul 
through a crossing of the circuit-wires, or some such acci¬ 
dent, which makes the resistance of the external circuil 
almost nothing, and allows an immense current to flow, 
which would burn out the armature in a few moments. 
Many machines are protected by devices which automati¬ 
cally open the circuit when this happens, but when this is 
not the case, the best plan is to instantly stop the excita¬ 
tion, if the dynamo is shunt or compound wound, bjj 
breaking the field circuit, or by breaking the main cir¬ 
cuit if the machine is series excited. A short circuit is i 


CARE OF THE DYNAMO. 


57 


instantly recognized by the flashing at the commutator, 
the squeaking, or throwing off - of the belt which it pro¬ 
duces. One should be very vigilant in avoiding short 
circuits. A dynamo should always be started and brought 
up to the proper speed before its field is excited, and 
before it is connected to the circuit; this is to test the 
lubrication, condition of the belt, and engine regulation. 
Care should be taken that there are no loose iron articles 
lying about too close to the dynamo, as they are likely to 
injure the armature, being drawn into it by the magnetic 
attraction. The circuit or circuits which the machine is 
to supply should first be tested (see later) ; and it should 
be ascertained that no one is at work upon the circuits, 
especially if the voltage used is a dangerous one. If the 
machine is of the constant potential type (see p. 48), the 
field circuit should then be completed, and the excita¬ 
tion gradually increased by slowly removing from the 
field circuit the rheostat, or resistance, which is always 
supplied with such machines. The rheostat is usually a 
fire-proof box containing coils of resistance wire, which 
are connected to a series of contact plates upon the front 
of the box, to the extreme one of which one side of the 
field circuit is connected. A pivoted arm connected to 
the other side of the field circuit is made to sweep over 
these contact plates, making connection with them succes¬ 
sively when rotated, and thus including in the field circuit 
more or less of the resistance, thereby regulating the field 
current. (Ohm’s Law.) When the proper voltage has 
been reached, as shown by the voltmeter (see p. 59), the 
machine may be connected to the circuit. More or less 
adjusting of the rheostat is usually necessary from time 
to time to keep the voltage at the proper amount; and 
it should, therefore, be located in a convenient place near 
the voltmeter. The ammeter (see p. 60) shows the cur- 


58 


ELECTRICITY FOR ENGINEERS. 


rent, in amperes, which the machine is sending out, and 
should be watched with a view of preventing an over¬ 
load. Constant current machines are usually started by 
simply closing the main circuit after the machines have 
been brought up to the proper speed. In shutting, 
down a shunt or compound machine the rheostat should' 
be gradually turned back, and the field circuit finally 
broken. It should then be disconnected from the circuit. 
Constant current machines are usually shut down by sim¬ 
ply opening the main circuit, although short circuiting the 
fields is a more safe method. 

When it is required to run more than one constant 
potential dynamo upon the same circuit, some care is 
necessary. The machines should preferably be of exactly 
the same size and type, and it should never be attempted 
with alternating current machines. In case one of the 
machines is running upon the circuit and it is required to 
add another, the machine added should be excited up to 
exactly the voltage of the circuit, and then connected with 
the other machine. It may then be loaded to the proper* 
point by increasing its excitation a little. It is of the 
utmost importance that the direction of the e.m.f. of 
the new machine is the same as those already in circuit, 
The load should be properly divided between the different 
machines. This is done by the rheostats. Increasing,? 
the excitation of any machine increases its load, and I 
decreasing its excitation decreases its load. 

It may be well to make a few suggestions concerning 
testing. The only apparatus which is usually at hand for 
this purpose is the magneto bell —a very handy, although! 
not a very exact instrument. It is simply a small hand* 
dynamo, and a bell such as is used in every telephone' 
outfit. When its two terminals are connected through a 
resistance which is not too high, and the handle turned,. 
the bell rings. 


CARE OF THE DYNAMO. 


59 


A dynamo should be frequently tested to see that the 
armature and field wire is properly insulated from the 
| iron frame of the machine. If by connecting one ter¬ 
minal of the magneto to any part of the iron frame and 
| the other to the armature or field wire a “ring” can be 
[produced, it shows that the insulation has broken down, 
and the defective part — armature or field, as the case 
may be — should either be shipped back to the factory for 
repairs, or repaired on the spot if possible. A few hours 
before being started, every circuit should be tested for 
“grounds” by attaching one terminal of the magneto to 
a gas or water pipe, or any other good conductor con¬ 
nected to the ground, and the other terminal successively 
to the two wires of the circuit. If a “ ring” can be pro¬ 
duced, it shows the circuit to be grounded. The trouble 
ought to be removed before the circuit is started. An arc 
circuit should always be tested a short time before start¬ 
ing up to see that it is complete — as it always should be. 
One should be able to ring through the entire circuit when 
the two terminals of the magneto are connected to the 
two circuit wires. When a number of circuits go out from 
the same dynamo room and run closely together for some 
distance, it is well to test to see that there is no connec¬ 
tion between separate circuits, such as might be caused 
by a “ cross.” This may be done by connecting one ter¬ 
minal of the magneto to both sides of one of the circuits, 
and the other magneto terminal to both sides of the other 
circuit. One should not be able to “ ring ” if the circuits 
are properly insulated from one another. This should be 
tried until each circuit is found to be insulated from every 
other one. The voltmeter and ammeter have already 
been alluded to as instruments for measuring the e.m.f. 
and the current. 

The voltmeter is a very high resistance instrument, and 


60 


ELECTRICITY FOR ENGINEERS. 


its terminals are connected to the points of a circuit be¬ 
tween which it is desired to know the e.m.f. acting. In 
dynamo rooms it is generally arranged with its terminals 
permanently connected to the two main conductors which 
feed the external circuit. The ammeter is a very low re¬ 
sistance instrument, and is connected so that the whole 
current passes through it. In dynamo rooms it is “ cut 
in” to one ot the main conductors leading from the 
dynamo. Care should be taken never accidentally to 
allow it to be connected to points having an e.m.f. 
between them. 

The electrical defects which are likely to arise in dyna¬ 
mos are of several kinds. In the first place the insulation 
of the armature conductors may prove defective either by 
having been injured mechanically or having been charred 
by overheating. If wires of different coils become con¬ 
nected, owing to this cause, or if there are connections - 
established between the winding and the iron core at 
more than one point, heavy useless currents will flow 
through these internal short circuits, which will heat thj 
armature so excessively and cause so much sparking as to 
render it unfit for use, If the armature happens to be of 
the ring form, with the coils not overlapping one another, 
it is generally possible to locate the trouble and remedy ; 
it by re-insulating the injured parts. But if it is a cylin¬ 
der armature, in which the coils overlap each other, it isl 
usually necessary to send it back to the factory to be re¬ 
wound, unless, indeed, the defect happens to be upon the 
surface, where it can be gotten at. 

Sometimes one may locate the defects in an armature 
by running it with no load, but with excited fields for a 
short time, and noticing which coils become most heated. 
These coils give a clew to where the trouble lies. A 
contact between two or more commutator connections is I 


CARE OF THE DYNAMO. 


61 


a defect of almost the same kind. If it is discovered 
before the heating which is produced has spoiled the in¬ 
sulation of the short-circuited coils, the trouble can gen- 

7 O 

erally be remedied by re-insulating or by cleaning out the 
copper dust which may have formed the connection. 
This trouble is best located by the heating as just de¬ 
scribed. When the circuit through an armature coil is 
opened by the fusing or breaking of the wire, or by a 
commutator connection becoming broken or detached 
from the bar, serious sparking is produced between the 
two commutator bars to which the broken coil is con¬ 
nected. This coil may be located by running the ma¬ 
chine with a load until the sparking has blackened the 
particular bars belonging to the damaged coil. If the 
break is in the commutator connection, or if in one of 
the coils of a ring armature, it would not be very difficult 
to make the needed repairs. It may be said in regard to 
armature troubles that it is very hard and unsatisfactory 
•work to. attempt to remedy any but the most trivial ones. 
One usually has not the facilities for conveniently and 
safely handling anything so heavy as a large armature. 
Besides, it is necessary to take off the band wires, if any 
coil is to be removed, and it is very difficult to replace 
them properly without the special machinery used at the 
factory. It is often better not to attempt any armature 
repairs except, perhaps, such slight ones as replacing a 
broken commutator connection or re-insulating some spot 
in the winding which is easily reached. It is far better 
to have a spare interchangeable armature for each kind of 
machine, to be used while the defective one is away at the 
factory being repaired. Every one should be able to find 
out, however, what the trouble in an armature is. 

Repairing defective field spools is not so difficult, as the 
method of winding is simple, A fielc^ spool may have 


4 


62 ELECTRICITY FOR ENGINEERS. 

its winding accidentally connected to the frame of the 
machine, perhaps grounding the circuit. If more than 
one such connection is formed, it will cause part of the field 
wire to be left out of circuit, causing sparking, and, in a 
shunt machine, heating of the spools. Or the field wire 
may become broken, making it impossible to excite the 
field. Enough has been said of the use of the magneto 
to enable one to recognize these troubles. 

Unless the point where the trouble lies is very near the 
outside of the winding, it is well to arrange the field spool 
in a lathe to hasten the process of unwinding and rewind¬ 
ing. The defect can usually be found and remedied with¬ 
out much trouble, the insulation made secure, and the same 
number of turns of the same sized wire replaced as have 
been removed. While considering the fields, we are nat¬ 
urally led to mention the matter of non-excitation, or the 
failure of a machine to supply current for its own fields. - 
This failure in constant potential machines may be caused 
by the field circuit being accidentally broken, either in. 
the spools, the rheostat, or the connecting wires. It is 
well to go over all the connections carefully, tightening 
them securely if they need it. A shunt excited machine, 
if its armature is “ dead short-circuited,” will not excite its ; 
fields. This should be looked to carefully. Sometimes 
the brush-holders may be found accidentally connected 
together by both touching a part of the frame, or some 
other similar accident may have occurred. Constant 
current machines, which are series wound, may usually 
be started, if they give trouble, by short-circuiting the \ 
dynamo terminals with a piece of heavy copper wire for 
a small part of a second and then removing it. 

The entire circuit, including the machine itself, should 
first be ascertained to be complete. For a full discussion 
of dynamo troubles, see “ Practical Management of Dyna¬ 
mos and Motors,” by Crocker & Wheeler, 


INCANDESCENT LIGHTING. 


63 


HEAVY CURRENT APPLICATIONS. 

INCANDESCENT ELECTRIC LIGHTING. 

The production of light by raising a conductor of high 
resistance to a white heat with an electric current is the 
principle of the incandescent lamp. Every one is familiar 


r * 



(carbon filament, or wire, heated in a glass bulb from which 
(the air has been exhausted as completely as possible. In¬ 
candescent lamps are almost always supplied with current 
from constant potential machines (p. 48). The lamps are 
I connected “ in parallel” across the constant potential con¬ 
ductors coming from the dynamo. The filament of each 
(lamp being subjected to the same voltage, and the lamps 
(being all alike, each one will receive the same amount of 

























64 


ELECTRICITY FOR ENGINEERS. 


electrical energy and therefore burn with the same bril 
liancy, and be independent of all the others. In Fig 
11, D represents a constant potential dynamo, froir 
which extend the constant potential mains, MM 1 , which 
branch into the sub-mains, NN 1 and PP 1 ; these in turr 
are divided into the constant potential branches, QQ 1 



PP \ SS 1 , and TT 1 , which supply the lamps. This is an 
example of direct incandescent lighting in which there is 
a direct electrical connection from the dynamo to the 
lamps. In the transfor?ner or converter system, however, 
the arrangement is as in Fig. 12. D is a multipolar con¬ 
stant potential dynamo without a commutator, thus giving 
an alternating e.m.f., changing its direction perhaps two 
hundred times a second. Such a machine usually gives 



















INCANDESCENT LIGHTING. 


65 


a constant potential of about 1000 volts. MM 1 are con¬ 
stant potential, alternating current, 1000 volt mains, lead¬ 
ing from the dynamo. Wherever lights are required, 
| there is placed a transformer or converter, C, consisting 
[of an iron core wound with two separate insulated coils 
of wire;—one the primary, P, of many turns of rather 
fine wire, having its terminals connected directly across 
the 1000 volt mains, while the other, the secondary, of a 
few turns of coarser wire, has its terminals connected 
directly to the main house wire. In the secondary, and 
alternating e.m.f. of 50 or 100 volts, suitable for running 
lamps, is produced by induction , just as the shocking cur¬ 
rent in an ordinary medical coil is generated. As there is 
no electrical connection between the dangerous 1000 volt 
mains and the house wires, there is no chance for acci¬ 
dents to persons having to do with the lamps. The 
advantage of using converters is that the high voltage 
current from the machine (1000 volts) may be transmitted 
for a much longer distance upon a certain sized wire with 
a certain amount of loss than could a low voltage current 
of say 100 volts, representing the same amount of power, 
and used to supply lamps direct. 

Less money has therefore to be expended for copper 
wire in the transformer system. 

Although it has been stated that incandescent lamps are 
arranged upon constant potential circuits, yet it is not 
really possible to keep the voltage between the two 
wires exactly the same everywhere in the whole system. 
Every wire, however large, offers some resistance, and 
therefore some of the e.m.f. is used up in overcoming it. 
The number of volts used up in any wire is found by mul¬ 
tiplying its resistance in ohms by the current flowing in 
amperes (see Ohm’s Law). This loss in volts is called 
the drop , and th ftper cent drop is the drop in volts divided 



66 


ELECTRICITY FOR ENGINEERS. 


by the voltage of the circuit. It is customary to allow a 
certain per cent drop, which must not be exceeded at any 
lamp in the system. The wires are then so proportioned 
as to give the proper resistance to secure the above result. 
Of course the drop is greatest at the time when all thei 
lamps are burning, and the full current required by all the 
lamps should be used in figuring it. The drop should 
never be large enough to make a noticeable difference in 
brilliancy between lamps at times of heavy and of light 
loads. In buildings it is common to allow from one to 
five per cent drop in voltage as the maximum. Referring 
to Fig. 11, part of the drop, perhaps two per cent, would 
be allowed to take place in the mains, another per cent 
in the sub-mains, and very little in the branches. 

The total drop to the lamps would then be a little over 
three per cent when all were burning. In order to be 
able to ascertain the size of wire required to run a certain 
number of lights taking a certain current and located at a 
certain distance, with a certain drop, it is convenient to 
use the following formula : — 

Area cross section of conductor required in circular 
21 4 L C N 

mils =—-, where L is the length in feet of the re¬ 

quired wire for one side of the circuit, C is the current in 
amperes required by each lamp, N is the number of lamps 
to be operated, and D is the drop in volts allowed when all 
are burning. The current which any lamp requires may 
be found approximately by multiplying its candle power 
by 3.5 and dividing the product by the voltage employed. 
The result of the above formula is obtained in circular 
mils of cross section, and it is only necessary to consult 
the wire table and find the size of wire most nearly cor¬ 
responding to this cross section. For example : Suppose’ : 
we wish to run ten 32 candle-power lamps at the end of a 



INCANDESCENT LIGHTING. 


67 

branch, one side of which requires 100 feet of wire; sup¬ 
pose the voltage to be 100, and the drop allowed to be two 
per cent, or two volts : — 

09 W O K 

I Current required by each lamp =——--— = 1.12 
kmperes. ^0 

21.4x100x1.12x10 11nQ , . , 

Then -—-= 11984 circular mils. 

No. 10 (B. and S. gauge) wire is seen by the table to 
have a cross section 10,382 circular mils, and is the size 
nearest to that required. 

Many important points relative to incandescent light¬ 
ing installations, including the careful insulation of the 
whole circuit, the best and safest methods of constructing 
it, the use only of fire-proof fittings, and indeed all the 
precautions necessary to secure the best results, are treated 
of among the rules of the Fire Insurance Underwriters rela¬ 
tive to electric wires, to which the reader is confidently 
referred. No heavy current installation should ever be 
made that does not conform in every particular to these 
excellent instructions. 

In order to avoid danger from fire in incandescent light¬ 
ing, as well as to avoid danger to the dynamo or trans¬ 
former by overloading, fusible cut-outs (/q Fig. 11) are 
used to automatically open the circuit and interrupt the 
current when it becomes unduly large in any wire. If, for 
instance, the circuit wires, having the full voltage between 
them, accidentally become connected together, forming a 
short circuit, an immense current would flow in them, and 
in the absence of the fusible cut-out, heating or even melt¬ 
ing them, and perhaps setting a serious fire, and at the 
same time injuring the dynamo or transformer. When 
each wire, however, has included in it a fuse , placed in a 
fire-proof cut-out, the fuse melts upon an extraordinary 




68 


ELECTRICITY FOR ENGINEERS. 


increase oi current and opens the circuit before the wires, 1 
either of the circuit or the dynamo, become dangerously 1 
heated. These fuses are strips or wires made of an alloy ! 
having rather a high resistance and a low melting point.: 
They are made of sizes suitable to carry various currents, 
and melt if the rated current is much exceeded. There : 
should be fuses in each side of the mains as they leave 
the dynamo, in the beginning of each side of each sub- 
main, and in each wire of each branch. In case lamps are 
suspended from the ceiling, it is generally easy to supply 
each individual lamp with fuses. The fuse in each wire 
should be such as just to carry the current required. This 
current is easily found by counting the number of lamps 
fed by the wire in question, and multiplying by the current 
required by each. It is best never to arrange more than 
six or eight lights to be protected by a single cut-out; and 
care should be taken that fuses when “blown” are re¬ 
placed by ones of suitable capacity, not by heavy copper 
wire, as the writer has more than once seen done. 

Incandescent lamps are commonly made of the follow-^ 
ing candle powers : 10, 16, 20, 32, 50, 75, 100, and 150; and 
yoltages from 20 to 125 volts. The voltage of a lamp 
means the number of volts which has to be applied to the 
filament to cause it to give its rated candle power. Lamps 
require from three to four watts to be expended for each 
candle power of light produced. After a lamp has been 
burning some time the inside of the bulb begins to blacken, 
due to a deposit of carbon particles from the filament, the 
filament gradually wears away, and finally breaks. The ' 
lamp is then of no use and must be replaced by a new * 
one. The total length of time a lamp burns before 
breaking is called its life; and 16 C. P. lamps, consuming 
3.1 watts per candle, or a total of 50 watts each, ought 
to have, on the average, a life of 600 hours; while lampsi 



INCANDESCENT LIGHTING. 


69 


equiring four watts per candle may be expected to last at 
iast 1000 or 1200 hours. This amounts to saying that 
le less power a lamp takes to give its rated C. P. the 
poner it will have to be replaced, and vice versa. Thus 
pere are two expenses connected with incandescent light- 
ig which depend on one another — the cost of the power 
nd the cost of lamps. To secure the best economy 
be sum of these two expenses should be made as small 
s possible. It is found that this result is attained where 
ower is expensive by using an economical lamp, giving 
ay one C. P. for 3.1 watts, but where power is cheap a 
imp giving one C. P. for each 4 watts is best. Instead 
f changing lamps to vary the economy in power, the 
oltage supplied to the lamps may be slightly increased 
r decreased above or below the voltage for which they 
?ere intended, making in the first case a more economical 
ut shorter lived lamp, and in the latter one of longer life 
ut one less economical of power. Where power is very 
xpensive and 4-watt lamps have been installed, it is some- 
imes good economy to run them a little above the proper 
oltage, but never so much above as to cause them to give 

bluish light. If the cost of power is small or next to 
othing, it is well to keep down the lamp breakage by 
unning the lamps a little below voltage, but not so much 
s to burn yellow. 

It is best to mark each new lamp when put into service 
nth the date ; in this way the life of a lamp may be ap- 
roximately ascertained. It is easy of course to tell how 
mch power a lamp uses by means of voltmeter and am- 
feter of suitable size. The wearing away of the filament 
nd the blackening of the bulb are gradual processes ; and 
s they progress the lamp gives less and less light, but, 
nfortunately, does not take proportionately less power, 
t is poor economy, especially where power is high, to run 


70 


ELECTRICITY FOR ENGINEERS. 


old lamps after they have begun to burn at a dull yello\ 
or orange. They had better be thrown away. The bes 
lighting effect is obtained from incandescent lamps b 
arranging them tip downward or in a slightly obliqu 
position under metallic or china reflectors. One of th< 
great advantages of the incandescent lamp is that it ma; 
be placed to throw its light where most needed. Ii 
lighting rooms of ordinary height, one 16 C. P. lamp fo 
each 80 sq. ft. of floor space will give good illumination 
and it is better, except where appearance is of great im 
portance, to distribute the lamps about uniformly, hanging 
them on pendants from the ceiling, rather than arranging 
them in clusters upon one or two fixtures. Nothing wil 
be said of the switches introduced into circuits to maki 
and break the current and thus control the lights; of thi 
sockets into which the lamps screw automatically making 
connection with the circuit; or of the various kinds o 
shades, globes, and other fittings which are used in in 
candescent lighting. They are easily understood an( 
applied. 


THE ARC LIGHTING SYSTEM. 

When a current of electricity is made to pass from one 
carbon point to another, through a small air gap, a ven 
brilliant light is given out by the intensely heated ends o 
the carbons, and by the arc, as the highly heated carbod 
vapor between them is called. The heat produced is o 
course due to the high resistance which the space betweer 
the carbon points offers to the current. (See p. 4.) 

A pair of such carbon points, suitably supported, enc 
to end, with mechanism for automatically starting the arc 
by separating the carbons and maintaining them at si 



ARC LIGHTING. 


VI 


uniform distance apart, is an arc lamp. The carbons of 
iarc lamps gradually burn away when in use, the upper 
carbon being arranged to burn about twice as fast as the 
flower one, and to feed downward automatically to keep 
Ithe length of the arc uniform, the lower carbon remain- 
ling stationary. This feeding of the carbon, as well as 
the starting of the arc, is accomplished by allowing the 
smooth brass rod which carries the upper carbon to 
[pass through a friction-clutch. This clutch is generally 
jmounted upon a lever, the raising or lowering of which 
separates the carbons or allows them to approach one 
another. An electromagnet suitably wound, acting 
jagainst a spring, controls the position of this lever, and 
Automatically starts and maintains the arc at its proper 
[length. Sometimes the upper carbon is carried upon a 
[rack, the position of which is controlled by the electro- 
Imagnet. Unfortunately there is such variety in the con- 
istruction of arc lamps of different makers that nothing 
imore than the foregoing general statement will be given. 
Arc lamps are usually arranged to burn in series; that is, 
the same current passes through each of them in succes¬ 
sion ; the wire coming from one terminal of the dynamo 
is connected, say, to the upper carbon of the first lamp, 
the lower carbon of this lamp is connected to the upper 
carbon of the second lamp, and so on. The wire from 
the lower carbon of the last lamp in circuit goes back to 
the other terminal of the dynamo. Ordinary arc lamps, 
which are rated at 2000 C. P., require a current of ten 
amperes and about 45 volts each, one lamp thus con¬ 
suming about 0.6 of an electrical H. P. The dynamos 
used in arc lighting are usually series excited and of the 
constant current type (see p. 48). 

The voltage produced increases as more lamps are in¬ 
cluded in the circuit, and decreases as lamps are cut out, 


12 


ELECTRICITY FOR ENGINEERS. 


thus keeping the current of a uniform strength. This 
regulation is usually automatically accomplished by shift¬ 
ing the brushes so as to vary the e.m.f. given to the cir¬ 
cuit, but it is sometimes done by automatically varying 
the field excitation. To give good service, an arc lamp 
should be kept perfectly clean, especially lamps that use 
a rod to carry the upper carbon. This rod should be 
thoroughly rubbed with a handful of clean waste each da) 
when the carbons are replaced, or, in other words, when 
the lamp is trimmed. Only the best carbons should be 
used in order to obtain a steady white light, and care 
should be taken in trimming the lamps to get the carbons 
in good alignment so that they will not slip by and ex¬ 
tinguish the light. An upper carbon ought to burn from 
seven to eight hours. If a lamp hisses continuously when 
burning, it shows that the arc is too short, and if a lamp 
burns blue, and flames, the arc is evidently too long. In 
most lamps the length of the arc may be regulated b) 
adjusting the spring which acts upon the clutch mechan¬ 
ism in opposition to the electromagnet. A loose clutch 
may be the cause of an unduly short arc, while a dirty car¬ 
bon rod may account for an arc that is too long or very 
irregular. Arc lamps should always be hung out of ordi¬ 
nary reach, as the voltage is usually dangerous, being 
2500 in a circuit capable of running 50 lamps. There is 
always a danger that the circuit may be grounded, and 
it is best that the public should not be able to handle 
it. The distribution of light, moreover, from lamps placed 
rather high is very favorable. Each lamp should have a 
switch arranged to completely disconnect it from the cir¬ 
cuit, so that the attendant may handle it safely while the 
rest of the lamps are running. Care should especially be 
taken that an arc circuit is never opened accidentally, as 
all the lamps are extinguished if the circuit is broken at J 


TRANSMISSION OF POWER. 


73 

any point. In connecting new lamps to the circuit, or 
starting up a new circuit, it is important to see that the 
lamps are burning “ right side up. 11 The current should 
be in such a direction that the upper carbon is most rapidly 
consumed, showing an intensely bright hollow on the 
end, called a crater. The lower carbon should be pointed. 
If lamps are burned wrong side up, the lower carbon 
holders are likely to be burned and the distribution of 
light very poor. 

A smoked or dark-colored glass should be kept on hand 
through which to watch the arc without injury to the eyes. 

The Underwriters 1 Rules give instruction for installing 
arc apparatus, and these rules should be carefully followed. 
The size of wire generally used for arc circuits is No. 6 
B. & S. gauge. 


TRANSMISSION OF POWER. 

If a dynamo be suitably furnished with electrical 
energy, its armature will revolve and transform a greater 
or less part of the energy thus supplied it into useful 
mechanical power, suitable for running any sort of ma¬ 
chinery. A reversed dynamo so running is an electric 
motor, and furnishes a ready means of transmitting 
mechanical power from place to place along an electric 
circuit. 

Either a shunt or series dynamo may be used as a 
motor, and it may be operated upon either a constant cur¬ 
rent or a constant potential circuit. The shunt motor 
operated upon a circuit of constant potential (usually 500 
volts) is so universally used for stationary power pur¬ 
poses that it alone will be treated of. Street car motors 
are usually series wound, and operated upon 500 volt 
circuits. 



74 


ELECTRICITY FOR ENGINEERS. 


The revolution of a motor armature by energy supplied 
it is due to the same forces which act against the revolu¬ 
tion of a dynamo armature — the attraction and repulsion 
of the armature conductors by the field ; and when a motor 
is in operation there is also the same action as in a 
dynamo, the production of an e.m.f. by its armature con¬ 
ductors cutting the field. This e.m.f. is nearly equal to 
and in the opposite direction from the e.m.f. of the cir¬ 
cuit upon which the machine is running, and therefore 
tends to reduce the current that passes through the motor 
armature, which is usually of so low resistance that, were 
this “ back e.m.f.” not present, a sufficiently large current 
would flow in the armature to injure it immediately. 

It is thus important for the safety of a motor never to 
allow its armature to be connected to the circuit (unless j 
properly protected) when this back e.m.f. is for any 
reason absent, which is, of course, the case when the 
field is not excited, and also the case until the armature 
has begun to revolve, for in neither instance are the ar¬ 
mature conductors cutting lines of force. In starting a 
shunt motor, the fields may be excited before the arma¬ 
ture is connected to it, so that the moment the armature 
begins to revolve it will begin to generate a back e.m.f., 
while to compensate for the lack of the back e.m.f. 
before the armature starts, a rheostat of suitable resist¬ 
ance is connected in series with the armature, and gradu¬ 
ally entirely “ cut out 11 as the machine speeds up; this 
cuts down the current which would otherwise flow, so 
that the armature is in no danger. It is of great impor¬ 
tance, especially with a shunt motor, to be sure that the 
armature circuit is open and that the resistance of the 
rheostat is all in before the machine is in anyway con¬ 
nected to the circuit. It is well, too, in doubtful cases, 1 
after the field circuit is closed, to test the field with a 


TRANSMISSION OF POWER. 


75 

piece of iron to show that it is excited. It is safe then to 
. close the armature circuit through all the rheostat resist¬ 
ance. All the connections of the field circuit should be 
very carefully made, to avoid the possible breaking of 
the field current while the motor is running. In case, 
as sometimes happens, the supply of current from the 
circuit ceases while the motor is in use, the machine 
should immediately be disconnected from the circuit and 
the rheostat turned back to the starting position with all 
its resistance in, otherwise, should the circuit start up 
again, it would find the motor stopped and without a back 
e.m.f., and damage might result. Automatic devices are 
made which protect motors from damage due to this cause 
or careless starting. 

Motors should be protected by the best form of fusible 
cut-outs, with fuses properly proportioned to carry the 
full load current of the machine. A motor should never 
be overloaded by requiring it to do unduly heavy work, 
causing the current which it takes from the circuit to be 
so much increased as to produce dangerous heating or 
sparking. An ammeter should be provided in circuit 
with the machine, so that the full load current, as stamped 
upon the machine by the maker, may never be exceeded 
without the fact being evident. A good shunt motor 
ought to run at nearly constant speed (within 5%) at all 
loads less than its maximum; and a machine running at 
not too high a speed is preferable, as it may be belted 
direct to the work, thus dispensing with the use of coun¬ 
ter-shafting in many cases, and requiring a little less at¬ 
tention. It is generally better also to purchase a motor 
which is somewhat larger than there is immediate use for, 
in order to allow for an increase in the load. 

Reasonably constant voltage of the supply circuit should 
be demanded from company furnishing the power, as with- 


76 


ELECTRICITY FOR ENGINEERS. 


out constant voltage the shunt motor loses one of its 
great advantages — its nearly uniform speed. 

Since a motor is nothing more nor less than a reversed 
dynamo, it requires the same care in securing a good place 
for it, in looking after the commutator, brushes, and bear¬ 
ings, and in preventing damage to it by overload or other¬ 
wise. 1 It may be stated that in almost all respects a good 
dynamo makes a good motor, and vice versa. In wiring 
for and installing a motor, the Underwriters 1 Rules upon 
the subject should be conscientiously followed, and, as in 
the case of incandescent lamps, the proper size of wire 
for the purpose is easily found by the use of the following 
formula: — 

Circular mils of cross section of_15964 N L 

required wire E V Y 

where N is the number of H. P. for which the motor is 
intended, L the length of one side of the required circuit, 
E the voltage of the circuit, V the drop in volts, and Y 
the efficiency of the motor, or the fraction of the electrical 
energy supplied it which is changed into useful mechanical 
power. For example : Suppose the motor to be a 10 H. P. 
machine of .9 efficiency, to be run from a 220-volt circuit, 
with a drop of 5 volts, and that 100 feet of wire are re¬ 
quired for each side of the circuit leading to it. Then 

Circular mils = i 5 ^ 4 ^ 1 0 - ^ 1 ? 0 = 16125. 
.9X5X220 

No. 8 B. & S. gauge wire is seen by the wire table to 
have a cross section of 16510 circular mils, and is there¬ 
fore the size nearest to the one required. 

As to the efficiency of electric motors, it is quite safe to 
expect 85 % efficiency from fully loaded motors larger than 

1 Motors are too often left to take care of themselves under conditions 
very unfavorable to their successful operation. 




THE STORAGE BATTERY. 


77 


one or two H. P., and even 90% is not uncommon in large 
machines doing their rated H. P. The remarks made con¬ 
cerning dynamo losses, and concerning the relations be¬ 
tween first cost, weight, size, and efficiency of dynamos, 
are also true of motors. The instructions concerning the 
detection and remedy of the various troubles to which 
dynamos are subject also apply here. 


THE STORAGE BATTERY. 

Storage Batteries are beginning to be largely em¬ 
ployed in connection with electric plants, and are likely 
in the near future to prove of immense practical impor¬ 
tance, as they furnish a means of storing electrical energy, 
acting to all intents and purposes as electrical reservoirs, 
which, when filled, may be drawn upon as required. A 
storage battery consists of a number of storage cells con¬ 
nected as are ordinary battery cells — generally in series. 
Each cell usually consists of a suitable jar filled with dilute 
sulphuric acid, in which are placed two sets of prepared lead 
plates, one set being made of spongy lead, and the other 
of lead oxide supported upon metallic lead. When a cur¬ 
rent of electricity is passed in the proper direction through 
such a batjery, the plates and acid are altered chemically in 
several ways ; but the principal change is the production of 
hydrogen and oxygen gas, the former being absorbed bv the 
spongy lead plate, and the latter entering into chemical 
combination with the lead oxide of the other plate. This 
chemical action represents the expenditure of a certain 
amount of electrical energy, and may be changed back 
into the electrical form at will, to be used for any desired 
purpose. 



78 ELECTRICITY FOR ENGINEERS. 

Passing a current from a dynamo or other source 
through the battery is called “ charging,” and when the 
chemical process which it produces is complete the bat¬ 
tery is said to be “charged.” The dynamo may then be 
disconnected, the battery connected to an electric circuit, 
and it will give out during its discharge an amount of 
electrical energy equal to 70 or 80 % of that which was 
furnished it by the dynamo. It is evident that storage 
batteries are of great value in electric lighting plants 
which are intended to furnish a continuous service, but 
where it is not economical to operate the machinery all 
the time. In such a plant the dynamo is operated during 
only a portion of the day, supplying the lights and char¬ 
ging the battery simultaneously. The dynamo may then 
be shut down and the battery left to take care of the load 
during the rest of the day, thus reducing the amount of 
attendance required by the plant. Other valuable appli¬ 
cations of the storage battery are readily suggested. Each 
storage cell furnishes an electromotive force of about two 
volts, and has a very low internal resistance, on which 
account a cell should never be short-circuited, as the 
current delivered would be enormous and would seriously 
injure the plates. 

In charging a storage battery certain precautions must 
be observed. Before connecting the dynamo to the Bat¬ 
tery it should be running at its normal speed, and should 
have its fields excited so that it gives a" voltage just equal 
to that of the battery. This may readily be determined 
by means of a voltmeter. It is of the greatest importance 
to be certain, before the dynamo and battery are con¬ 
nected, that the electromotive forces which they produce 
are in opposite directions, otherwise a short-circuit of the 
worst description will be the result. It is easy to deter¬ 
mine the direction of the electromotive force acting in any 




THE STORAGE BATTERY. 


79 


circuit by means of a small pocket-compass and the appli- 
■ cation of the following rule: Arrange a portion of one of 
the wires of the circuit horizontally in a south and north 
direction; place it directly over the compass needle, and 
if the electromotive force is acting from south to north, 
the north pole of the comparss will turn to the west . 1 

If the foregoing directions are carefully observed, the 
dynamo and battery may safely be thrown together, and 
the voltage of the dynamo raised sufficiently to cause it to 
deliver the proper strength of current to the battery. If 
the dynamo is excited to a voltage less than that of the 
battery, the battery will discharge through it, running it as 
a motor. This state of things may be detected by noting 
which is the loose and which the tight side of the dynamo 
belt, thereby determining whether the dynamo is doing 
work or is having work done upon it. It is necessary that 
the speed of the dynamo be very constant, as otherwise it 
may decrease sufficiently to allow the voltage to fall below 
that of the battery, when the state of things just described 
would be attained. It is of great advantage to have an 
automatic switch arranged to open the circuit, in case the 
current reverses from its proper direction. Even an indi¬ 
cator arranged to ring a bell if this happens is a useful device. 

The strength of the current furnished the battery dur¬ 
ing charging is a matter of some importance. It should 
never be so great as to cause the cells to give off much 
gas, except during the latter part of the process. A better 
efficiency is obtained from the battery if the charging cur¬ 
rent is so small as to not cause the cells to gas at all, but 
a much longer time is required to complete the process. 
Charging may be considered to be complete when tl;e 
cells gas violently even on a reduced current. 

o J 

1 The initial letters of the principal words of this rule form the word 


SNOW, 


80 


ELECTRICITY FOR ENGINEERS. 


The current which flows during discharge ought gene¬ 
rally to be less than the charging current, and the dis¬ 
charge of a battery should not be carried so far as to J 
cause its voltage to rapidly diminish. A storage battery 
in good condition, with good insulation, ought to retain 

its charge for months if not used. A slight loss, due to 
<=> . ® 
leakage and other causes, is, however, inevitable. A bat¬ 
tery ought not to be left for any great length of time in a 
discharged condition. The acid used in the cells ought 
to be kept at the strength prescribed by the makers. The 
strength is indicated by the specific gravity, which may be 
measured by a hydrometer. 

The voltage of each individual cell should frequently be 
tested by means of a suitable voltmeter, and any cell 
which falls much below the average should be carefully 
examined, in order to locate the trouble. A short-circuit 
among the plates is very likely to have happened, caused 
by the falling from its lead supports of some of the mate¬ 
rial in such a way as to bridge plates of opposite polarity. 
Possibly the cell may not have had so much charging as 
the others for some reason. It is best to have several 
extra cells on hand to take the places of any which may 
have to be removed. 

The storage cells and the shelves upon which they rest 
should be kept perfectly dry and clean ; and it is important 
that the battery be placed in a room where good ventila¬ 
tion is provided, as corrosive vapor and explosive gases 
are evolved during charge, which ought immediately to be 
disposed of. The contacts between the cells ought to 
be frequently inspected, with the view of keeping them 
firm and bright. The Insurance Underwriters’ Rules in 
regard to storage batteries and circuits leading from them 
should be strictly followed, 





underwriters’ rules. 


81 


PART III. 

RULES AND REQUIREMENTS. 

AS RECOMMENDED BY THE UNDERWRITERS’ INTERNATIONAL 
ELECTRIC ASSOCIATION, AND ADOPTED BY THE 
UNDERWRITERS’UNIONS OF THE DIFFERENT 
CITIES OF THE UNITED STATES, 

GENERAL SUGGESTIONS. 

The use of wire ways for rendering concealed wiring 
permanently accessible is most heartily indorsed and rec¬ 
ommended, and this method of accessible concealed con¬ 
struction is advised for general use. 

Architects are urged, when drawing plans and specifica¬ 
tions, to make provision for the channelling and pocket¬ 
ing of buildings for electric light or power wires ; and in 
specifications for electric gas lighting, to require a two- 
wire circuit, whether the building is to be wired for elec¬ 
tric lighting or not, so that no part of the gas fixtures or gas 
piping be allowed to be used for the gas-lighting circuit. 

Wires that are to be concealed will not be approved 
unless sufficient time is given for this Union to make a 
complete inspection before the floors are laid, laths put on, 
or the wires concealed in any other manner. 

If notice is sent to the office of the local inspector by 
the wire contractors when work is begun, there will be 
no delay in inspecting. 


82 


ELECTRICITY FOR ENGINEERS. 


CLASS A. 

CENTRAL STATIONS. 

FOR LIGHT OR POWER. 

These Rules also apply to Dynamo Rooms in Isolated Plants , 
connccted.with or detached from buildings used for other 
purposes : also to all varieties of apparatus 
therein of both high and low potential . 

1. Generators — 

a. Must be located in a dry place. 

b. Must be insulated on floors or base frames, which 
must be kept filled, to prevent absorption of moisture, and 
also kept clean and dry. 

c. Must never be placed in a room where any hazardous 
process is Carried on, nor in places where they would be 
exposed to inflammable gases or flyings or combustible 
material. 

d. Must each be provided with a waterproof covering. 

2. Care and Attendance. —A competent man must 
be kept on duty in the room where generators are 
operating. 

Oily waste must be kept in approved metal cans, and 
removed daily. 

Approved waste cans shall be made of metal, with legs 
raising can three inches from the floor, and with self-clos¬ 
ing covers. 

3. Conductors. — From generators, switch-boards, 

rheostats, or other instruments, and thence to outside 
lines, conductors— * 

a. Must be in plain sight, and readily accessible. 


underwriters’ rules. 


83 


b. Must be wholly on non-combustible insulators, such 
as glass or porcelain. 

c. Must be separated from contact with floors, parti¬ 
tions, or walls through which they may pass by non-com¬ 
bustible insulating tubes, such as glass or porcelain. 

d. Must be kept rigidly so far apart that they cannot 
come in contact. 

e. Must be covered with non-inflammable insulating 
material sufficient to prevent accidental contact, except 
that “ bus bars” may be made of bare metal. 

f. Must have ample carrying capacity, to prevent heat¬ 
ing. (See Capacity of Wires Table.) 

4. Switch-boards—. 

a. Must be so placed as to reduce to a minimum the 
danger of communicating fire to adjacent combustible 
material. 

Special attention is called to the fact that switch-boards 
should not be built down to the floor, nor up to the ceil¬ 
ing; but a space of at least eighteen inches, or two feet, 
should be left between the floor and the board, and be¬ 
tween the ceiling and the board, in order to prevent fire 
from communicating from the switch-board to the floor or 
ceiling, and also to prevent the forming of a partially con¬ 
cealed space very liable to be used for storage of rubbish 
and oily waste. 

b. Must be accessible from all sides when the connec¬ 
tions are on the back; or may be placed against a brick 
or stone wall when the wiring is entirely on the face. 

c. Must be kept free from moisture. 

d. Must be made of non-combustible material, or of 
hard wood in skeleton form, (filed to prevent absorption 
of moisture. 


84 


ELECTRICITY FOR ENGINEERS. 


e. Bus bars must be equipped in accordance with Rule 3 
for placing conductors. 

5. Resistance Boxes and Equalizers — 

a. Must be equipped with metal or other non-combus¬ 
tible frames. 

The word “ frame ” in this section relates to the entire 
case and surrounding of the rheostat, and not alone to the 
upholding supports. 

b. Must be placed on the switch-board, or, if not 
thereon, at a distance of a foot from combustible material, 
or separated therefrom by a non-inflammable, non-absorp- 
tive, insulating material. 

6. Lightning Arresters— 

a. Must be attached to each side of every overhead cir¬ 
cuit connected with the station. 

b. Must be mounted on non-combustible bases in plain 
sight on the switch-board, or in an equally accessible 
place, away from combustible material. 

c. Must be connected with at least two “ earths 11 by 
separate wires, not smaller than No. 6 B. & S , which 
must not be connected to any pipe within the building. 

d. Must be so constructed as not to maintain an arc 
after the discharge has passed. 

7. Testing — 

a. All series and alternating circuits must be tested 
every two hours while in operation, to discover any leakage 
to earth, abnormal in view of the potential and method 
of operation. 

b. All multiple arc low potential systems (300 volts or 
less) must be provided with an indicating or detecting 


UNDERWRITERS’ RULES. 


85 


device, readily attachable, to afford easy means of testing 
where the station operates continuously. 

c. Data obtained from all tests must be preserved for 
examination by insurance inspectors. 

These rules on testing to be applied at such places as 
may be designated by the association having jurisdiction. 

MOTORS . 

8. Motors — 

a. Must be wired under the same precautions as with a 
current of the same volume and potential for lighting. 
The motor and resistance box must be protected by a 
double pole cut-out, and controlled by a double pole 
switch. 

b. Must be thoroughly insulated, mounted on filled dry 
wood, be raised at least eight inches above the surround¬ 
ing floor, be provided with pans to prevent oil from soak¬ 
ing into the floor, and must be kept clean. 

c. Must be covered with a waterproof cover when not 
in use, and, if deemed necessary by the inspector, be en¬ 
closed in an approved case. 

From the nature of the question, the decision as to 
what is an approved case must be left to the inspector 
to determine in each instance. 

9. Resistance Boxes — 

a . Must be equipped with metal or other non-combusti¬ 
ble frames. 

The word “frame” in this section relates to the entire 
case and surrounding of the rheostat, and not alone to 
the upholding supports. 

b. Must be placed on the switch-board, or at a distance 
of a foot from combustible material, or separated there¬ 
from by a non-inflammable, non-absorptive, insulating 
material, 


86 


ELECTRICITY FOR ENGINEERS. 


CLASS B. 

ARC (SERIES) SYSTEMS. 

OVER 3 OO VOLTS. 

Any circuit attached to any machine, or combination of 
machines, which develops over 300 volts difference of po¬ 
tential between any two wires, shall be considered as a 
high potential circuit, and coming under that class, unless 
an approved transforming device is used, which cuts the 
difference of potential down to less than 300 volts. 

10. Outside Conductors. — All outside overhead 
conductors (including services) — 

a. Must be covered with some approved insulating 
material, not easily abraded, firmly secured to properly 
insulated and substantially built supports, all tie wires 
having an insulation equal to that of the conductors they 
confine. 

Insulation that will be approved for service wires must 
be solid, at least of an inch in thickness, and covered 
with a substantial braid. It must not readily carry fire, 
must show an insulating resistance of one megohm per 
mile after two weeks 1 submersion in water at 70 degrees 
Fahrenheit, and three days 1 submersion in lime-water, 
with a current of 550 volts, and after three minutes 1 elec¬ 
trification. 

b. Must be so placed that moisture cannot form a cross- 1 
connection between them, not less than a foot apart, and 
not in contact with any substance other than their insu¬ 
lating supports. 

c. Must be at least seven feet above the. highest point 
of flat roofs, and at least one foot above the ridge of 


UNDERWRITERS RULES. 


87 


pitched roofs over which they pass, or to which they are 
attached. 

d. Must be protected by dead insulated guard irons or 
wires from possibility of contact with other conducting 
wires or substances to which- current may leak. Special 
precautions of this kind must be taken where sharp angles 
occur, or where any wires might possibly come in contact 
with electric light or power wires. 

e. Must be provided with petticoat insulators of glass 
or porcelain. Porcelain knobs or cleats and rubber hooks 
will not be approved. 

f. Must be so spliced or joined as to be both mechani¬ 
cally and electrically secure without solder. The joints 
must then be soldered, to insure preservation, and covered 
with an insulation equal to that on the conductors. 

All joints must be soldered, even if made with the 
McIntyre or any other patent splicing device. This rul¬ 
ing applies to joints and splices in all classes of wiring 
covered by these Rules. 

11. Service Blocks — 

a. Must be covered over their entire surface with at 
least two coats of waterproof paint. 

b. Telegraph, telephone, and similar wires must not be 
placed on the same cross-arm with electric light or power 
wires. 

INTERIOR CONDUCTORS. 

12. All Interior Conductors — 

a. Must be covered where they enter buildings from 
outside terminal insulators to and through the walls with 
extra waterproof insulation, and must have drip loops out¬ 
side. The hole through which the conductor passes must 




88 


ELECTRICITY FOR ENGINEERS. 


be bushed with waterproof and non-combustible insulat¬ 
ing tube or hard rubber tube, slanting upward toward the 
inside. The tube must be sealed with tape, thoroughly 
painted, and securing the tube to the wire. 

b. Must be arranged to enter and leave the building 
through a double contact service switch, which will effect¬ 
ually close the main circuit and disconnect the interior 
wires when it is turned “ off.” The switch must be so 
constructed that it shall be automatic in its action, not 
stopping between points when started, and prevent an 
arc between the points under all circumstances ; it must 
indicate on inspection whether the current be “on” or 
“ off,” and be mounted in a non-combustible case, and 
kept free from moisture and easy of access to police or 
firemen. 

c. Must be always in plain sight, and never encased, 
except when required by the inspector. 

d. Must be covered in all cases with an approved non¬ 
combustible material that will adhere to the wire, not 
fray by friction, and bear a temperature of 150 degrees- 
Fahrenheit without softening. 

Insulation that will be approved for interior conductors 
must be solid, at least ^ of an inch in thickness, and 
covered with a substantial braid. It must not readily 
carry fire, must show an insulating resistance of one 
megohm per mile after two weeks’ submersion in water 
at 70 degrees-Fahrenheit, and three days’ submersion in 
lime-water, with a current of 550 volts, and after three 
minutes’ electrification. 

e. Must be supported on glass or porcelain insulators, 
and kept rigidly at least eight inches from each other, 
except within the structure of lamps, or on hanger boards, 
cut-out boxes, or the like, where less distance is necessary. 


underwriters’ rules. 


89 


; f. Must be separated from contact with walls, floors, 
umbers, or partitions through which they may pass by 
aon-combustible insulating tube or hard rubber tube. 

1 g. Must be so spliced or joined as to be both mechani¬ 
cally and electrically secure without solder. They must 
then be soldered to insure preservation, and covered with 
an insulation equal to that on the conductors. 


LAMPS AND OTHER DEVICES. 

13. Arc Lamps —In every case — 

a. Must be carefully isolated from inflammable material. 

b. Must be provided at all times with a glass globe sur¬ 
rounding the arc, securely fastened upon a closed base. 
No broken or cracked globes to be used. 

" c. Must be provided with an approved hand switch, 
also an automatic switch, that will shunt the current 
around the carbons should they fail to feed properly. 

The hand switch to be approved , if placed anywhere 
except on the lamp itself, must comply with requirements 
for switches on hanger boards as laid down in Section ( g ). 

d. Must be provided with reliable stops to prevent car¬ 
bons from falling out in case the clamps become loose. 

e. Must be carefully insulated from the circuit in all 
their exposed parts. 

f. Must be provided with a wire netting around the 
globe, and an approved spark arrester above, to prevent 
escape of sparks, melted copper or carbon, where readily 
inflammable material is in the vicinity of the lamps. It is 
recommended that plain carb'ons, not copper plated, be 
used for lamps in such places. 

An approved spark arrester is one which will so close 


90 


ELECTRICITY FOR ENGINEERS. 


tbe upper orifice of the globe, that it will be impossible fo: 
any sparks thrown off* by the carbons to escape. 

g. Hanger boards must be so constructed that all wire: 
and current-carrying devices thereon shall be exposed t( 
view, and thoroughly insulated by being mounted on s 
waterproof, non-combustible substance. All switches 
attached to the same must be so constructed that the) 
shall be automatic in their action, not stopping betweer 
points when started, and preventing an arc between points 
under all circumstances. 

14. Incandescent Lamps in Series Circuits Having 

a Maximum Potential of 300 Volts or over — 

a . Must be governed by the same rules as for arc lights, 
and each series lamp provided with an approved hand¬ 
spring switch and automatic cut-out. 

b. Must have each lamp suspended from a hanger 
board by means of a rigid tube. 

c. No electro-magnetic device for switches, and no sys¬ 
tem of multiple-series or series-multiple lighting will be 
approved. 

d. Under no circumstances can series lamps be attached 
to gas fixtures. 


CLASS C. 

INCANDESCENT (LOW PRESSURE) SYSTEMS. 

300 VOLTS OR LESS. 

OUTSIDE CONDUCTORS. 

15. Outside Overhead Conductors — 

a. Must be erected in accordance with the rules for arc 
(series) circuit conductors. 

b. Must be separated not less than 12 inches, and be 


UNDERWRITERS 5 ’ RULES. &1 

provided with an approved fusible cut-out that will cut off 
the entire current as near as possible to the entrance to 
the building and inside the walls. 

An approved fusible cut-out must comply with the 
sections of Rules 23 and 24 describing fuses and cut-outs. 

The cut-out required by this section must be placed so 
as to protect the switch required by Rule 17. 

! 16. Underground Conductors — 

a. Must be protected against moisture and mechanical 
j injury, and be removed at least two feet from combustible 
l material when brought into a building, but not connected 

with the interior conductors. 

b. Must have a switch and a cut-out for each wire be¬ 
tween the underground conductors and the interior wiring 
when the two parts of the wiring are connected. 

These switches and fuses must be placed as near as 
possible to the end of the underground conduit, and con¬ 
nected therewith by specially insulated conductors, kept 
apart not less than two and a half inches. 

The cut-out required by this section must be placed so 
as to protect the switch. 

c. Must not be so arranged as to shunt the current 
through a building around any catch-box. 

INSIDE WIRING. 

GENERAL RULES. 

17. — At the entrance of every building there shall be an 
approved switch placed in the service conductors by which 
the current may be entirely cut off. 

The switch required by this rule to be approved must 
be double pole, must plainly indicate whether the current 





ELECTRICITY FOR ENGINEERS. 


&2 

is “ on” or “ off,” and must comply with Sections a , c, d ’ 
and e of Rule 26 relating to switches. 

18. Conductors — 

a. Must have an approved insulating covering, and must 
not be of sizes smaller than No. 14 B. & S.; No. 16 B. 
W. G., or No. 4 E. S. G., except that, in conduit installed 
under Rule 22, No. 16 B. & S., No. 18 B. W. G., or No. 
4 E. S. G., may be used. 

In so-called “ concealed ” wiring, moulding, and con¬ 
duit work, and in places liable to be exposed to dampness, 
the insulating covering of the wire, to be approved , must 
be solid, at least h of an inch in thickness, and covered 
with a substantial braid. It must not readily carry fire, 
must show an insulating resistance of one megohm per 
mile after two weeks’ submersion in water at 70 degrees 
Fahrenheit, and three days’ submersion in lime-water, with 
a current of 550 volts, and after three minutes’ electrifica¬ 
tion. 

For work which is entirely exposed to view throughout 
the whole interior circuits, and not liable to be exposed 
to dampness, a wire with an insulating covering that will 
not support combustion, will resist abrasion, is at least T X g 
of an inch in thickness, and thoroughly impregnated with 
a moisture repellent, will be approved. 

b. Must be protected when passing through floors, or 
through walls, partitions, timbers, etc-., in places liable to 
be exposed to dampness, by waterproof, non-combustible, 
insulating tubes, such as glass or porcelain. 

Must be protected when passing through walls, parti¬ 
tions, timbers, etc., in places not liable to be exposed to 
dampness, by approved insulating bushings especially made 
for the purpose. 

Except for floors, and for places liable to be exposed 


underwriters’ rules. 


93 


to dampness, glass, porcelain, metal-sheathed interior 
conduit, and vulca tube, when made especially for bush¬ 
ings, will be approved. The two last named will not be 
approved if cut from the usual lengths of tube made 
for conduit work, nor when made without a head or 
flange on one end. 

c. Must be kept free from contact with gas, water, or 
other metallic piping, or any other conductors or conduct¬ 
ing material which they may cross (except high potential 
conductors), by some continuous and firmly fixed non¬ 
conductor creating a separation of at least one inch. 
Deviations from this rule may sometimes be allowed by 
special permission. 

d. Must be so placed in crossing high potential con¬ 
ductors that there shall be a space of at least one foot at 
all points between the high and low tension conductors. 

e. Must be so placed in wet places, that an air space will 
be left between conductors and pipes in crossing, and the 
former must be run in such a way that they cannot come 
in contact with the pipe accidentally. Wires should be 
run over all pipes upon which condensed moisture is likely 
to gather, or which by leaking might cause trouble on a 
circuit. 

SPECIAL RULES. 

19. Wiring not Encased in Moulding or Approved 
Conduit — 

a. Must be supported wholly on non-combustible in¬ 
sulators, constructed so as to prevent the insulating cover¬ 
ings of the wire from coming in contact with other 
substances than the insulating supports. 

b. Must be so arranged that wires of opposite polarity, 
with a difference of potential of 150 volts or less, will be 
kept apart at least two and one-half inches. 


u 


ELECTRICITY FOR ENGINEERS. 


c. Must have the above distance increased proportion¬ 
ately where a higher voltage is used, unless they are en¬ 
cased in moulding or approved conduit. 

d. Must not be laid in plaster, cement, or similar finish. 

e. Must never be fastened with staples. 

In Unfinished Lofts, between Floor and Ceil¬ 
ings, in Partitions and other Concealed Places — 

f. Must have at least one inch clear air space surround¬ 
ing them. 

g. Must be at least ten inches apart when possible, 
and should be run singly on separate timbers or studding. 

h. Wires run as above immediately under roofs, in 
proximity to water tanks or pipes, will be considered as 
exposed to moisture. 

i. Wires must not be fished for any great distance, and 
only in places where the inspector can satisfy himself 
that the above rules have been complied with. 

j. Twin wires must never be employed in this class of 
concealed work. 

20. Mouldings — 

a. Must never be used in concealed work or in damp 
places. . 

b. Must have at least two coats of waterproof paint, or 
be impregnated with a moisture repellent. 

c. Must be made of two pieces, a-backing and capping, 
so constructed as to thoroughly enckse the wire, and 
maintain a distance of one-half inch between conductors 
of opposite polarity, and afford suitable protection from 
abrasion. 


Underwriters’ rules. 


95 


21. Special Wiring — 

In breweries, packing-houses, stables, dyehouses, paper 
and pulp mills, or other buildings specially liable to mois¬ 
ture or acid, or other fumes liable to injure the wires or 
insulation, except where used for pendants, conductors — 

a. Must be separated at least six inches. 

b. Must be provided with an approved waterproof 
covering. 

The insulating covering of the wire to be approved 
under this section must be solid, at least -g 3 T of an inch in 
thickness, and covered with a substantial braid. It must 
not readily carry fire, must show an insulating resistance 
of one megohm per mile after two weeks’ submersion in 
water at 70 degrees Fahrenheit, and three days’ submer¬ 
sion in lime-water, with a current of 550 volts, after three 
minutes’ electrification, and must also withstand a satis¬ 
factory test against such chemical compounds or mixtures 
as it will be liable to be subjected to in the risk under 
consideration. 

c. Must be carefully put up. 

d. Must be supported by glass or porcelain insulators. 
No switches or fusible cut-outs will be allowed where ex¬ 
posed to inflammable gases or dust, or to flyings of com¬ 
bustible material. 

e. Must be protected when passing through floors, 
walls, partitions, timbers, etc., by waterproof non-com¬ 
bustible, insulating tubes, such as glass or porcelain. 

22. Interior Conduits 1 — 

a. Must be continuous from one junction box to an¬ 
other, or to fixtures, and must be of material that will 

1 The object of a tube or conduit is to facilitate the insertion or extrac¬ 
tion of the conductors, to protect them from mechanical injury, and, as far 


ELECTRICITY FOR ENGINEERS. 


96 


resist the fusion of the wire or wires they contain, without 
igniting the conduit. The American Circular Loom Co. 
Tube, the metal-sheathed Interior Conduit Tube, and the 
Vulca Tube are approved for the class of work called for 
in this rule. 

b. Must not be of such material or construction that the 
insulation of the conductor will ultimately be injured or 
destroyed by the elements of the composition. 

c. Must be first installed as a complete conduit system, 
without conductors, strings, or anything for the purpose 
of drawing in the conductors, and the conductors then to 
be pushed or fished in. The conductors must not be 
placed in position until all mechanical work on the build¬ 
ing has been, as far as possible, completed. 

d. Must not be so placed as to be subject to mechani¬ 
cal injury by saws, chisels, or nails. 

e. Must not be supplied with a twin conductor, or two 
separate conductors, in a single tube. 

f. Must have all ends closed with good adhesive mate¬ 
rial, either at junction boxes or elsewhere, whether such 
ends are concealed or exposed. Joints must be made air¬ 
tight and moisture-proof. 

g. Conduits must extend at least one inch beyond the 
finished surface of walls or ceilings until the mortar or 
other similar material be entirely dry, when the projection 
may be reduced to half an inch. 

23. Double Pole Safety Cut-outs — 

a. Must be in plain sight, or enclosed in an approved 
box, readily accessible. To be approved, boxes must be 

as possible, from moisture. Tubes or conduits are to be considered merely 
as raceways, and are not to be relied on for insulation between wire and wire, 
or between the wire and the ground. 


underwriters’ rules. 


07 


constructed, and cut-outs arranged, whether in a box or 
not, so as to obviate any danger of the melted fuse metal 
coming in contact with any substance which might be 
ignited thereby. 

b. Must be placed at every point where a change is 
made in the size of the wire (unless the cut-out in the 
larger wire will protect the smaller). 

c. Must be supported on bases of non-combustible, in¬ 
sulating, moisture-proof material. 

d. Must be supplied with a plug (or other device for 
enclosing the fusible strip or wire) made of incombustible 
and moisture-proof material, and so constructed that an 
arc cannot be maintained across its terminals by the fus¬ 
ing of the metal. 

e. Must be so placed that on any combination fixture 
no group of lamps requiring a current of six amperes or 
more shall be ultimately dependent upon one cut-out. 
Special permission may be given in writing by the in¬ 
spector for departure from this rule in case of large chan¬ 
deliers . 

f. All cut-out blocks must be stamped with their maxi- 
mum safe carrying capacity in amperes, and when in¬ 
stalled must be marked with the current they are intended 
to carry. 

24. Safety Fuses — 

a . Must all be stamped or otherwise marked with the 
number of amperes they will carry indefinitely without 
melting. 

b. Must have fusible wires or strips (where the plug 
or equivalent device is not used), with contact surfaces 
or tips of harder metal, soldered or otherwise, having 
perfect electrical connection with the fusible part of the 


ELECTRICITY FOR ENGINEERS. 


strip, whenever they have a carrying of ten (io) amperes 
or over. 

c. Must all be so proportioned to the conductors they 
are intended to protect, that they will melt before the max¬ 
imum safe carrying capacity of the wire is exceeded. 

25 . Table of Capacity of Wires — 

It must be clearly understood that the size of the fuse 
depends upon the s.ize of the smallest conductor it pro¬ 
tects, and not upon the amount of current to be used on 
the circuit. Below is a table showing the safe carrying 
capacity of conductors of different sizes in Birmingham, 
Brown & Sharpe, and Edison gauges, which must be fol¬ 
lowed in the placing of interior conductors : — 


Brown & Sharpe. 
Gauge 


No. Amperes. 

oooo. 175 

000. 145 

00 . 120 

o . 100 

1 . 95 

2 . 70 

t . 60 

4 . 5 ° 

5 . 45 

6 . 35 

7 •••'.. 30 

8 . 25 

10. 20 

12 . 15 

14 .. IO 


26 . Switches — 


Birmingham. 

Gauge 

No. Amperes. 


OOOO .. 

. 175 

OOO _ 

. *5° 

00. 

. 130 

0 . 

_ no 

I . 

- 95 

2 . 

. 85 

3 . 

.... 75 

4 . 

. 65 

5 . 


6 . 

- 5 ° 

7 . 

.... 45 

8 . 

•••• 35 

10 . 

.... 3° 

12 . 


14 . 

. 15 

16 . 


18 . 

. 5 

20 . 



Edison 

Standard. 

Gauge 

No. 

Amperes. 

200 .. 

. 175 

180 .. 

. 160 

140 

. 135 

no 

. no 

9 ° .... 

. 95 

80 .... 

. 85 

65 .... 

. 75 

55 .... 

. 65 

50 .... 

. 60 

40 .... 

. 5 ° 

3 ° .... 

. 4 ° 

25 .... 

. 35 

20 .... 

. 3 ° 

12 .... 


8 .... 

. 15 

5 .... 



3 . 5 

2 . 3 


a. Must be mounted on moisture-proof and non-com¬ 
bustible bases, such as slate or porcelain. 

b. Must be double pole when the circuits which they 






















































underwriters’ rules. 


99 

control supply more than six 16 candle power lamps, or 
their equivalent. 

c. Must have a firm and secure contact, must make and 
break readily, and not stop when motion has once been 
imparted by the handle. 

d. Must have carrying capacity sufficient to prevent 
heating. 

e. Must be placed in dry, accessible places, and be 
grouped as far as possible, being mounted — when prac¬ 
ticable— upon slate or equally non-combustible back 
boards. Jackknife switches, whether provided with fric¬ 
tion or spring stops, must be so placed that gravity will 
tend to open rather than close the switch. 

27. Fixture Work — 

a. In all cases where conductors are concealed within 
or attached to gas fixtures, the latter must be insulated 
from the gas-pipe system of the building by means of 
approved joints. The insulating material used in such 
joints must be of a substance not affected by gas and that 
will not shrink or crack by variation in temperature. In¬ 
sulating joints with soft rubber in their construction will 
not be approved. 

Insulating joints, to be approved, must be entirely made 
of material that will resist the action of illuminating gases, 
and will not give way or soften under the heat of an 
ordinary gas flame. They shall be so arranged that a 
deposit of moisture will not destroy the insulating effect, 
and shall have an insulating resistance of 250,000 ohms 
between the gas-pipe attachments, and be sufficiently 
strong to resist the strain they will be liable to in attach¬ 
ment. 

b. Supply conductors, and especially the splices to fix- 


100 


ELECTRICITY FOR ENGINEERS. 


ture wires, must be kept clear of the grounded part of 
gas-pipes; and where shells are used, the latter must be 
constructed in a manner affording sufficient area to allow 
this requirement. 

c. When fixtures are wired outside, the conductors must 
be so secured as not to be cut or abraded by the pressure 
of the fastenings or motion of the fixture. 

d. All conductors for fixture work must have a water¬ 
proof insulation that is durable and not easily abraded, 
and must not in any case be smaller than No. 18 B. & S., 
No. 20 B. W. G., No. 2 E. S. G. 

e. All burrs or fins must be removed before the con¬ 
ductors are drawn into a fixture. 

f. The tendency to condensation within the pipes 
should be guarded against by sealing the upper end of 
the fixture. 

g. No combination fixture in which the conductors are 
concealed in a space less than one-fourth inch between 
the inside pipe and the outside casing will be approved. 

h. Each fixture must be tested for “ contacts ” between 
conductors and fixtures, for “ short circuits,” and for 
ground connections before the fixture is connected to its 
supply conductors. 

i. Ceiling blocks of fixtures should be made of insulat¬ 
ing material; if not, the wires in passing through the 
plate must be surrounded with hard rubber tubing. 

28. Arc Lights on Low Potential Circuits — 

a. Must be supplied by branch conductors not smaller 
than No. 12 B. & S. gauge. 

b. Must be connected with main conductors. only 
through double pole cut-outs. 


underwriters’ rules. 


101 


c. Must only be furnished with such resistances or 
regulators as are enclosed in non-combustible material, 
such resistances being treated as stoves. 

Incandescent lamps must not be used for resistance 
devices. 

d . Must be supplied with globes and protected as in 
the case of arc lights on high potential circuits. 

29. Electric Gas Lighting. 

Where electric gas lighting is to be used on the same 
fixture with the electric light — 

a. No part of the gas piping or fixture shall be in elec¬ 
trical connection with the gas-lighting circuit. 

b. The wires used with the fixtures must have a non- 
inflammable insulation, or, where concealed between the 
pipe and shell of the fixture, the insulation must be such 
as required for fixture wiring for the electric light. 

c. The whole installation must test free from “ grounds.” 

d. The two installations must test perfectly free from 
connection with each other. 

30. Sockets — 

a. No portion of the lamp socket exposed to contact 
with outside objects must be allowed to come into elec¬ 
trical contact with either of the conductors. 

b. In rooms where inflammable gases may exist, or 
where the atmosphere is damp, the incandescent lamp 
and socket should be enclosed in a vapor-tight globe. 

31. Flexible Cord — 

a. Must be made of conductors, each surrounded with 
a moisture-proof and a non-inflammable layer, and fur¬ 
ther insulated from each other by a mechanical separa- 


102 


ELECTRICITY FOR ENGINEERS. 


tor of carbonizable material. Each of these conductors 
must be composed of several strands. 

b. Must not sustain more than one light not exceeding 
50 candle power. 

c. Must not be used, except for pendants, wiring of fix¬ 
tures, and portable lamps or motors. 

d. Must not be used in show windows. 

e. Must be protected by insulating bushings where the 
cord enters the socket. The ends of the cord must be 
taped to prevent fraying of the covering. 

f. Must be so suspended that the entire weight of the 
socket and lamp will be borne by knots under the bush¬ 
ing in the socket, and above the point where the cord 
comes through the ceiling block or rosette, in order that 
the strain may be taken from the joints and binding- 
screws. 

g. Must be equipped with keyless sockets as far as 
practicable, and be controlled by wall switches. 

CLASS D. 

ALTERNATING SYSTEMS. — CONVERTERS OR 
TRANSFORMERS. 

32. Converters — 

a. Must not be placed inside of any building, except 
the central station, unless by special permission of the 
underwriters having jurisdiction. 

b. Must not be placed in any but metallic or other non- 
conbustible cases. 

c. Must not be attached to the outside walls of build¬ 
ings, unless separated therefrom by substantial insulating 
supports. 


underwriters’ rules. 


103 


In those Cases where it may not be possible to 

EXCLUDE THE CONVERTERS AND PRIMARY WIRES EN¬ 
TIRELY from the Building, the following Pre¬ 
cautions MUST BE STRICTLY OBSERVED : — 

33. Converters— 

Converters must be located at a point as near as possi¬ 
ble to that at which the primary wires enter the building, 
and must be placed in a room or vault constructed of, or 
lined with, fire-resisting material, and used only for the 
purpose. They must be effectually insulated from the 
ground, and the room in which they are placed be prac¬ 
tically air-tight, except that it shall be thoroughly venti¬ 
lated to the outdoor air, if possible, through a chimney or 
flue. 

34. Primary Conductors — 

a. Must each be heavily insulated with a coating of 
moisture-proof material from the point of entrance to the 
transformer, and, in addition, must be so covered and 
protected that mechanical injury to them or contact with 
them shall be practically impossible. 

b. Must each be furnished, if within a building, with a 
switch and a fusible cut-out where the wires enter the 
building, or where they leave the main line, on the pole 
or in the conduit. These switches should be enclosed in 
secure and fireproof boxes, preferably outside the building. 

c. Must be kept apart at least ten inches, and at the 
same distance from all other conducting bodies when in¬ 
side a building. 

35. Secondary Conductors — 

a. Must be installed according to the rules for “ Low 
Potential Systems, ” 


104 


ELECTRICITY FOR ENGINEERS. 


CLASS E. 

ELECTRIC RAILWAYS. 

36. — All rules pertaining to arc light wires and stations 
shall apply (so far as possible) to street railway power 
stations and their conductors in connection with them. 

37. Power Stations — 

a. Must be equipped in each circuit as it leaves the sta¬ 
tion with an approved automatic “breaker” or other 
device that will immediately cut off the current in case the 
trolley wires become grounded. This device must be 
mounted on a fireproof base and in full view and reach of 
the attendant. 

Automatic circuit breakers should be submitted for 
approval before being used. 

38. Trolley Wires — 

a. Must be no smaller than No. 0, B. & S. copper or 
No. 4, B. & S. silicon bronze, and must readily stand the 
strain put upon them when in use. 

b. Must be well insulated from their supports, and, in 
case of the side or double pole construction, the supports 
shall also be insulated from the poles immediately outside 
of the trolley-wire. 

c. Must be capable of being disconnected at the power 
house, or of being divided into sections, so that, in case 
of fire on the railway route, the current may be shut off 
from the particular section, and not interfere with the work 
of the firemen. This rule also applies to feeders. 

d. Must be safely protected against contact with all 
other conductors. 


underwriters’ rules. 


105 


39. Car Wiring — 

a. Must be always run out of reach of the passengers, 
and must be insulated with a waterproof insulation. 

40. Lighting and Power from Railway Wires — 

a. Must not be permitted under any pretence in the 
same circuit with trolly wires with a ground return, nor 
shall the same dynamo be used for both purposes, except 
in street railway cars, electric car houses, and their power 
stations. 

41. Car Houses — 

Must have special cut-outs located at a proper distance 
outside, so that all circuits within any car house can be 
cut out at one point. 

42. Ground Return Wires 

Where ground return is used it must be so arranged 
that no difference of potential will exist greater than five 
volts to 50 feet, or 50 volts to the mile between any two 
points in the earth or pipes therein. 

CLASS F. 

43. Storage or Primary Batteries — 

a. When current for light and power is taken from pri¬ 
mary or secondary batteries the same general regulations 
must be observed as apply to similar apparatus fed from 
.dynamo generators developing the same difference of 
potential. 

b. All secondary batteries must be mounted on ap¬ 
proved insulators. 

Insulators for mounting secondary batteries to be ap¬ 
proved must be non-combustible, such as glass, or thor¬ 
oughly vitrified and glazed porcelain, 


106 


ELECTRICITY FOR ENGINEERS. 


c. Special attention is directed to the rules for rooms 
where acid fumes exist. 

d. The use of any metal liable, to corrosion must be 
avoided in connections of secondary batteries. 


MISCELLANEOUS. 

44. — a. The wiring in any building must test free from 
grounds; i.e., each main supply line and every branch 
circuit shall have - an insulation resistance of at least 
25,000 ohms, and should have an insulation resistance 
between conductors and between all conductors and the 
ground (not including attachments, sockets, receptacles, 
etc.) of not less than the following : — 


Up to 

10 

amperes. 


u 

2 5 

U 


ii 

5 ° 

ii 

. 800,000 

ii 

IOO 

ii 

. 300,000 

a 

200 

a 

. 160,060 

a 

400 

a 


a 

800 

a 


“ I 

,600 

a 



All cut-outs and safety devices in place in the above. 

Where lamp sockets, receptacles, and electroliers, etc., 
are connected, one half of the above will be required. 

b. Ground wires for lightning arresters of all classes 
and ground detectors must not be attached to gas pipes 
within the building. 

c. Where telephone, telegraph, or other wires connected 
with outside circuits are bunched together within any 
building, or where inside wires are laid in conduit or duct 
with electric light or power wires, the covering of such 
wires must be fire-resisting, or else the wires must be en¬ 
closed in an air-tight tube or duct. 











MISCELLANEOUS. 


107 


d. All conductors connecting with telephone, district 
messenger, burglar alarm, watch clock, electric time, and 
other similar instruments, must be provided near the 
point of entrance to the building with some protective 
device which will operate to shunt the instruments in case 
of a dangerous rise of potential, and will open the circuit 
and arrest an abnormal current flow. Any conductor nor¬ 
mally forming an innocuous circuit may become a source 
of fire hazard if crossed with another conductor, through 
which it may become charged with a relatively high 
pressure. 

e. The following formula for soldering fluid is sug¬ 
gested : — 


Saturated solution of zinc. 5 parts. 

Alcohol. 4 parts. 

Glycerine. i part. 


Materials.: — 

The following are given as a list of non-combustible, 
non-absorptive, insulating materials, and are listed 
here for the benefit of those who might consider hard 
rubber, fibre, wood, and the like, as fulfilling the above 
requirements. Any other substance which it is claimed 
should be accepted, must be forewarded for testing be¬ 
fore being put on the market: -— 

1. Thoroughly vitrified and glazed Porcelain. 

2. Glass. 

3. Slate without metal veins. 

4. Pure Sheet Mica. 

5. Marble (filled). 

6 . Lava (certain kinds of). 

7. Alberene Stone. 





108 


ELECTRICITY FOR ENGINEERS. 


Insulating Joints: — 

The mica joints of the following makes are approved : — 
E. P. Gleason Manufacturing Co., New York. 

W. T. C. Macallen Co., Boston. 

Thackara Manufacturing Co., Philadelphia. 

Wires : — 

The following list of wires have been tested, and found 
to comply with the requirements for an approved insula¬ 
tion under Rule 10 (#), Rule 12 (d), and Rule 18 (a). 
Americanite. 

Bishop. 

Canvasite. 

Clark. 

Columbia. 

Crescent. 

Crown. 

Edison Machine. 

Grimshaw (white core). 

Habirshaw (red core). 

Kerite. 

National India Rubber Co. (N. I. R). 

Okonite. 

Paranite. 

Raven Core. 

Safety Insulated 

Salamander (rubber covered). 

Simplex (caoutchouc). 

None of the above wires to be used unless protected 
with a substantial braided outer covering. 


TABLE OF DIMENSIONS AND RESISTANCES OF PURE COPPER WIRE* 


REVISED. 


NO. 

B. & S. 

DlAM. 

Mils. 

Area 

W’gt. & Length. 

Sp. GR. 8.9. 

No. 

B. 

& 

S. 

Resistance at 75° F. 

Lbs. per 
IOOOYt. 
INS’D H. B 
& H 

Line wire 

Ft. per lb. 
INS’D H. B. | 
& H 

Line wire. 

Circular 

Mils. 

Square 

Inches. 

Lbs. 

per 

1000 FT. 

Pounds 

per 

Mile. 

Feet 

per 

Pound. 

R Ohms 

per 

1000 FEET. 

Ohms 

PER MILE. 

Feet 

PER 

Ohm. 

Ohms 

per Pound. 

0000 

000 

00 

0 

460.000 

409.640 

364.800 

324.950 

211600.0 
167805.0 
133079 0 
105592.5 

166190.2 

131793.7 

104520.0 

82932.2 

640.73 
508.12 
402.97 

319.74 

. 3383.04 
• 2682.85 
2127.66 
1688.20 

1.56 

1.97 

2.48 

3.13 

4-0 

3-0 

00 

0 

.04904 

.06184 

.07797 

.09827 

.25891 

.32649 

.41108 

.51885 

20392.9 

16172.1 

12825.4 

10176.4 

.00007653 

.00012169 

.00019438 

.00030734 

800 

666 

500 

363 

1.25 

1.50 

2.00 

2.75 

1 

2 

3 

4 

6 

289.300 

267.630 

229.420 

204.310 

181.940 

83694.5 

66373.2 

52633.5 

41742.6 

33102.2 

65733.5 

52129.4 

41338.3 

32784.5 

25998.4 

253.43 

200.98 

169.38 

126.40 

100.23 

, 1338.10 
1061.17 
841.50 
667.38 
529.23 

3.95 

4.98 
6.28 
7.91 

9.98 

1 

2 

3 

4 

5 

.12398 

.15633 

.19714 

.24858 

.31346 

.65460 

.82543 

h04090 

1.31248 

1.65507 

8066.0 

6396.7 

5072.5 

4022.9 

3190.2 

.00048920 

.00077784 

.0012370 

.0019666 

.0031273 

313 

250 

200 

144 

125 

3.20 

4.00 

6.00 

6.9 

8.0 

6 

7 

8 

9 

10 

162.020 

144.280 

128.490 

114.430 

101.890 

26250.5 

20816.7 

16509.7 
13094.2 

10381.6 

20617.1 
16349.4 
12966.7 

10284.2 
8163.67 

79.49 

63.03 

49.99 

39.65 

31.44 

419.69 

332.82 

263.96 

209.35 

165.98 

12.58 

15.86 

20.00 

25.22 

31.81 

6 

7 

8 

9 

10 

.39528 

.49845 

.62849 

.79242 

.99948 

2.08706 

2.63184 

3.31843 

4.18400 

5.27726 

2529.9 

2006.2 

1591.1 

1262.0 

1000.5 

.0049728 

.0079078 

.0125719 

.0199853 

.0317046 

105 

87 

69 

50 

9.5 

11.5 

14.5 

20.0 

11 

12 

13 

14 

15 

90.742 

80.808 

71.961 

64.084 

57.068 

8234.11 

6529.94 

6178.39 

4106.76 

3266.76 

6467.06 

5128.60 

4067.09 

3225.44 

2567.85 

24.93 

19.77 

15.68 

12.44 

9.86 

131.65 

104.40 

82.792 

65.658 

52.069 

40.11 

50.58 

63.78 

80.42 

101.40 

11 

12 

13 

14 

15 

1.2602 

1.5890 

2.0037 

2.5266 

3.1860 

6.65357 

8.39001 

10.5798 

13.3405 

16.8223 

793.56 

629.32 

499.00 

395.79 

313.87 

. .0505413 

.08036*11 
.127788 
.203180 
.323079 

31 

22 

32.0 

45.0 

16 

17 

18 

19 

20 

60.820 

46.257 

40.303 

35.890 

31.961 

2582.67 

2048.20 

1624.33 

1288.09 

1021.44 

2028.43 

1608.66 

1275.75 

1011.60 

802.24 

7.82 

6.20 

4.92 

3.90 

3.09 

41.292 

32.746 

25.970 

20.594 

16.331 

127.87 

161.24 

203.31 
256.39 

323.32 

16 

17 

18 

19 

20 

4.0176 

5.0660 

6.3880 

8.0555 

10.1684 

21.2130 

26.7485 

33.7285 

42.5329 

53.6362 

248.90 

197.39 

156.54 

124.14 

98.44 

.513737 

.816839 

1.208764 

2.065312 

3.284374 

14 

11 

70.0 

90.0 

21 

28.462 

810.09 

636.24 

2.46 

12.952 

407.67 

21 

12.8088 

67.6302 

78.07 

5.221775 



22 

25.347 

642.47 

504.60 

1.95 

10.272 

514.03 

22 

16.1504 

85.2743 

61.92 

8.301819 



23 

22.571 

509.45 

400.12 

1.54 

8.1450 

648.25 

23 

20.3674 

107.540 

49.10 

13.20312 



24 

20.100 

404.01 

317.31 

1.22 

6.4593 

817.43 

24 ■ 

25.6830 

135.606 

38.94 

20.99405 



25 

17.900 

320.41 

251.65 

.97 

5.1227 

1030.71 

26 

32.3833 

170.984 

30.88 

33.37780 



26 

16.940 

254.08 

199.56 

.77 

4.0623 

1299.77 

26 

40.8377 

215.623 

24.49 

53.07946 



27 

14.195 

201.50 

158.26 

.61 

3.2215 

1638.97 

27 

61.4952 

271.895 

19.42 

84.39916 



28 

12.641 

159.80 

125.50 

.48 

2.6548 

2066.71 

28 

64.9344 

342.854 

15.40 

134.2005 



29 

I1.257 

126.72 

99.526 

.38 

2.0260 

2606.13 

29 

81.8827 

432.341 

12.21 

213.3973 



30 

10.025 

100.50 

78.933 

.30 

1.6068 

3286.04 

30 

103.245 

545.133 

9.686 

339.2673 



31 

8.928 

79.71 

62.603 

.24 

1.2744 

4143.18 # 

31 

130.176 

687.327 

7.682 

539.3404 



32 

7.950 

63.20 

49.639 

.19 

1.0105 

6225.26 

32 

164.174 

866.837 

6.091 

857.8498 



33 

7.080 

50.13 

39.369 

.15 

.8014 

6588.33 

33 

207.000 

1092.96 

4.831 

1363.786 



34 

6.304 

39.74 

31.212 

.12 

.6354 

8310.17 

34 

261.099 

1378.00 

3.830 

2169.776 



35 

6.614 

31.52 

24.753 

.10 

.5039 

10478.46 

36 

329.225 

1738.31 

3'037 

3449.770 



36 

6.000 

25.00 

19.635 

.08 

.3997 

13209.98 

36 

415.047 

2191.45 

2.409 

5482.766 



37 

4.453 

19.83 

15.574 

.06 

.3170 

16654.70 

37 

523.278 

2762.91 

1.911 

8715.030 



38 

3.965 

15.72 

12.347 

.05 

.2513 

21006.60 

38 

660.011 

3484.86 

1.515 

13864.51 



39 

3.531 

12.47 

9.7923 

.04 

.1993 

26487.84 

39 

332.228 

4394.16 

1.202 

22313.92 



40 

3.144 

9.88 

7.7635 

.03 

.1580 

33410.05 

40 

1049.718 

6542.51 

.9626 

35071.11 




* l mile pure copper wire 1-16 in. diam, — 13,59 ohms at 15.6°C or 59.9°F. 
























































































































. : r '. \$>y r - y'/ 


’ i 


1 .O 




Ou. ' - - 

C)U -Ul 



in ' 



. 





-4- 

*-• 

aurnj' 

A 

1 






n i- -:-- ~ — 

-. .. — 


---TT—-- 




' \/*. ' 


\> - 


V. 

(» 

^ r 

* «• 




} a* wt 


m-4-i :. ■ 


VX'-e & 





• , 



30.T* ,n> 



- 


' ,v$ 


* 




J*.3£S8 





■ ~— 


—r~-r™— 


* - % «•< 


tf&fiSD2 




y.80- Vr 





£ 



c 

? •• ■ 



- 








rr~rr 


-if o 


k: a&j 


, . 


*» . : 



.. 

•* % 





• 


-r • 










t r 

' q* ■* r 

JV 

N 


iV\'i * ' V'i-<i£ 

:p ■ :* '-S,.yJ: . 

•;< . 

it&r \ &k_ . „7 ■ 


i 




. / *• 

• -• / 



. < 

iii>a j,5tr 

•. • 









. ; ..c 


:■; 

IS ■ 

c« 

A*?- i 

• • v • • 

. r.;0.4-02 


. •* 


g 

£ as 

OSMM 


§ 


V. 

ft 


IM \ 



OSkftt 

I? 


098. it. r 

(I 


2K.0Q 

i it | 



or 

- •*> 

$£ V?*] 

>e • 

'* i* 
v i. 


’/) 


&:.&asa 

8o0. t*> 





T^> ‘Jl "'i 





. 1 


iv 

81 


T< 










• . v *- .1 



. ‘ ,* 

** 





>: 

1 


8.&- 

& 

.**' > 

■»>. 





■ *t 

u. > 

*^Cu-.y xfc 

il.O 

^C.T , & 

$ 

)%:<< ! ** 

■ ' ! -' > 


A 4’ 

( * f f 




*wi . m 

T* 

i (& 


M.j 1 C 

























ELECTRICITY FOR ENGINEERS. 


THE MASON REDUCING VALVE. 


This valve is designed to reduce and maintain an 
even steam or air pressure regardless of the initial press¬ 
ure. It will automatically reduce boiler pressure for 
steam-heating coils, dry rooms, paper-making machin¬ 
ery, slashers, dye kettles, and all places where it is 
desirable to use lower pressure than that of the boiler. 
The dash-pot, which immediately fills with condensa¬ 
tion, prevents all chattering or pounding, and requires 
no attention. No extra lock-up attachment is needed, 
as the pressure is regulated by a key, which the en¬ 
gineer retains. The sizes, up to and including 2 -inch, 
are made of the best composition, and above that, of 
cast iron, with composition linings. In the larger sizes, 
the composition lining is hung up in the valve, leaving 
a space between the iron and composition for the un¬ 
equal expansion of the metals. Thus there is no possibility of the piston 
sticking when the valve is heated. The area of the passage from the high 
to the low pressure side of the valve is equal, when open, to the full area of 
the pipe, so that a low pressure of the system, almost equal to the initial 
high pressure, may be carried. This valve will maintain an even steam or 
air pressure as low as one pound if necessary. This valve is warranted to do 
all that is claimed for it, and will be sent to responsible parties on 30 days’ 
trial. We make an iron valve for use with ammonia in ice-making machin¬ 
ery. 



SIZE 

PIFE 



PRICE LIST. 



PRICE. 

Vn inch 

9 


ft 0 . 

* , 

r 


$15.00 

% 

a 


» 

• 0 e 

ft O 

0 

• 

18.OO 

1 



0 

6 • • 

ft O 

• 

• 

22.00 

1 'A 

it 

• 

9 

0 J c 

ft ft 

• 

• 

28.00 

*y 2 

it 

0 

• 

, ft 

ft ft 

• 

• 

35 -°° 

» 

(3 

a 

9 

• O 5 

0 ft 

ft 

9 

44,00 


44 

• 


ft 

ft 

ft 

• 

57.00 

3 

i { 

„ 


ft ft 3 

ft ft 

* 

a 

72.00 

4 

U 



ft * c 

ft , 

« 

* 

100.00 

5 

44 

e 

0 

J 0 

c 

« 


135.00 

6 

€t 

0 

3 

ft ft » 

ft ft 


0 

180.00 

8 

it 

• 

a 

• 

0 


0 

250.00 


Manufactured by the MASON REGULATOR CO., Bpston, Mass, 



























ELECTRICITY FOR ENGINEERS. 


THE MASON PUMP PRESSURE REGULATOR. 

For Fire, Tank, Elevator, Air and Water Works 
Pumps, or any class of Pumping Machinery where 
it is necessary to maintain a constant pressure. The 
Mason Pressure Regulator is made upon an entirely new 
principle, the advantage of which is that the steam itself 
is made both to open and shut the valve. The Regulator 
may be instantly adjusted to any pressure desired by 
simply turning the key, as shown in the cut. 

The especial feature of this regulator is that the press¬ 
ure chamber into which the water enters is entirely 
removed and separate from the steam and all working 
parts. 

The long cylinder at the bottom of the regulator is a 
dash-pot, the piston of which is connected with the main 
valve of regulator, thereby preventing sudden and violent 
“jumping ” of the pump when the pressure suddenly changes. 

For automatic fire sprinkler service they have been fou - . d especially valua¬ 
ble, as the valve is thrown wide open, immediately the slightest drop in pres¬ 
sure occurs. On application we can refer parties where they are in use. 

These regulators are made in all the pipe sizes; those up to and including 
2 -inch, of the best steam metal; the larger sizes, of cast iron, lined with 
steam metal. The springs are made of the finest tool steel, tempered. 



SIZE PIPE, 
% inch 

% “ 

i 

" 


PRICE LIST. 


FKICB. 

, . $17.00 

< , 20.00 

, .> 25 .OO 

> : 30 OO 

, 3 42.00 

55.00 

, , 68.00 

„ , 85.00 

115.00 


Manufactured by the MASON REGULATOR CO , Boston, Mass. 
















ELECTRICITY FOR ENGINEERS. 


THE MASON LOCOMOTIVE REDUCING 
VALVE. 



This reducing valve has been in use by the leading 
steam car-healing companies for the last three years. 
During that time over 3,000 have been placed on 
nearly every railroad which has adopted steam heat. 
One feature which will commend itself to every engineer 
is the self-locking device, which enables the valve to be 
set for any pressure, and automatically locked. In the 
manufacture of this valve there is no attempt made to 
save on stock in order to cheapen the price. Every 
valve is made of the best steam metal, and will not 
steam-cut at a pressure of 180 pounds. As we supply a 
large number of car-heating and railroad companies, 
each of whom use different connections, we are pre¬ 
pared to furnish the sizes as follows : — 

The yi inch size, 

<< l it it 

“ 1 y K “ « ... 


PRICE. 

$18.00 

22.00 

28.00 


THE MASON AIR-BRAKE PUMP REGULATOR. 



This is constructed on the same principle as 
our pump pressure regulator, but with a few 
small changes, so as to allow of its application 
to air-brake pumps without changing the fit¬ 
tings on the locomotive. It is only necessary 
to pkce these in the steam pipe leading to the 
pump, and connect the air pressure pipe with 
the train service pipe. As the air chamber is 
entirely separate from the steam and working 
parts, any particles of dirt which may get into 
the main service pipe cannot get into the work¬ 
ing parts of the regulator and thence into the 
pump, neither can the steam and air pressure 
have access to each other. 

We will send one on trial to any railroad. 
Weight, with couplings, 8J4 pounds. 

Price, $15 net. 


Manufactured by the MASON REGULATOR CO., Boston, Mass. 

































ELECTRICITY FOR ENGINEERS. 


THE MASON PUMP GOVERNOR. 




The Mason Pump Governor 
is to the direct acting steam 
pump what the ordinary ball 
governor is to the steam engine. 
It attaches directly to the pis¬ 
ton rod of the pump, and oper¬ 
ates a balanced valve placed in 
the steam pipe, thereby exactly 
weighing the amount of steam 
to the needs of the pump, and 
economizing the same. By 
using the Mason Governor, you 
can instantly set or change your 
pump to any required speed, 
which will be maintained in spite 
of variation in load or steam 
fig. i. pressure. As all the working 

parts of the Governor are immersed in oil, the wear is reduced to a minimum. 
It is large’y used on vacuum pumps, deep-well pumps, water-works pumps, 
ice machines, and all classes of pumps requiring a uniform stroke. 

For duplex pumps, the Gover¬ 
nor is fitted with a special valve, 
which holds the main piston sta¬ 
tionary during the momentary 
pause of the pump piston, from 
which the motion is taken. 

For large duplex pumping en¬ 
gines a special Governor is made, 
fitted with double parts, and con- 
fig. 2 . nected with both piston rods, thus 

insuring perfect regulation for every portion of each revolution of the engine. 
Figure i sh ws the Governor unattached. 

Figure 2 shows the Governor connected with balanced valve. 


PRICE LIST OF GOVERNOR, WITHOUT VALVE. 


We make three sizes of these Governors: — 


Size No. 1 goes with J4 in. steam valve to 2 in. inc., 

(l (I H 1 / (( (( {| i ( 4 t ( ( 

2 2 y 2 4 

“ “ 3 “ “5 “ “ “ and upward, 


FRICK. 

$ 45.00 
60.00 
80.00 


Manufactured by the MASON REGULATOR CO., Boston, Mass- 















ELECTRICITY FOR ENGINEERS. 



THE MASON STEAM DAMPER REGULATOR 

Is made in accordance with an entirely novel princi¬ 
ple in the construction of damper regulators: the steam 
is admitted from the boiler, through a small strainer, as shown 
in the cut, under a diaphragm which is attached to an auxiliary 
valve, which either lets in the steam or excludes it from the 
piston which works in the cylinder. This piston, being forced 
up or down by the steam pressure, turns a wheel, from which 
runs the chain which is connected to the damper. 

By an ingenious arrangement, the damper is not 
throwm entirely open by the slightest change of 
pressure in the boiler, but is gradually opened, as 
the pressure changes, thereby 
not allowing sudden and great 
variations of draft, whereby the 
coal is wasted. 

We manufacture only one size. 

The regulators are made of the 
best steam metal throughout. 

Each one is nickel-plated. Weight, thirty 
pounds. Price, $ 80 , including bracket, 
weight, and twenty-five feet of chain. 

We manufacture our Lever and Balanced 
Valves, as shown on following page, in 
two different styles. The piston valves 
are not perfectly steam tight. The bevel-seated valves are intended for use 
where it is required for the valve to shut absolutely steam tight. 

Style A, Balanced Valve Piston, with straight stem guide. 

“ B, “ “ “ lever attachment. 

“ C, “ “ Bevel-seated, with straight stem guide. 

“ D, “ “ “ “ “ lever attachment. 


Manu r actured by the MASON REGULATOR CO., Boston, Mass 

























































ELECTRICITY FOR ENGINEERS. 


THE MASON BALANCED VALVE 



Is a double piston balanced valve, for use in connection with our speed gov¬ 
ernor, and for which we have found a ready sale in the many cases wheie 
such valves are used. The principal advantage of our valve is in the guide 
for the valve stem, which is cast on the bonnet, thereby keeping the valve 
stem in a direct line with the stuffing box. For this reason it is impossible 
for the valve stem to bend, and the packing seldom has to be renewed. The 
sizes up to 2 -inch are m<de of the best steam metal; above that, of cast 
iron, lined with steam metal. A knuckle-joint tapped for three-eighths rod 
is on the same stem of each valve. This saves expense n making connec¬ 
tions. 

THE MASON LEVER VALVE 



Is made essentially the same as the “ Mason 
Balanced Valve,” with the substitution of yoke 
and lever with weight attached, for the bonnet 
and knuckle-joint of the balanced valve. The 
lever valve will be found useful in controlling 
the supply of water in tanks by attaching to a 
ball float. It can also be used to control steam 
pumps in tank service, by placing the valve in 
the steam supply pipe to the pump, and con¬ 
necting the lever with the ball float placed in 
the tank. There is no lost motion in any of 
the joints, a fact which those desirous of close 
regulation will appreciate. These valves can 
be furnished either as piston or seated valves. 

The latter style is steam tight. For prices, see next page. 


Manufactured by the MASON REGULATOR CO., Boston, Mass. 











































































Electricity for engineers. 


PRICE LIST OF BALANCED AND LEVER VALVES. 


SIZE VALVE. 

Vi inch, 
3 /4 “ 


I 

I 

1 

2 

2 % 


K 

% 


U 

a 

<5 

a 

it 


3 

4 


a 

u 



PRICK, 

• $5-So 

6.50 
. 8.00 

o 9.00 

, 10.50 

. 15.00 

, 19.50 

. 25.00 

37-oc 


GABLE ADDRESS, “ MASQN 1 CA,” BOSTON. 


TELEGRAPH CODE. 


For quantity of goods wanted use numerals. 


Locomotive Reducing Valves, 


• 


# 

• 

Locomotive 

Pump Pressure Regulators, 


• • 

1 



* 

Pressure 

Lever Valves, 

• 


■ • 

• 


, 


Lever 

Pump Governors, . 



. , 

« 




Governor 

Balanced Valves, 

» 



• 


3 

0 

Balance 

Reducing Valves, , 

« 


P 



* 

0 

Reducer 

Damper Regulators, 

( 


; 1 

9 


O 

• 

Damper 

Air Brake Regulators* 

• 


SIZES. 

» 

9 

• 


Brake 

K inch, . . * 

• 


e 3 

9 


• 

3 

Madder 

% ... 

• 


• » 

• 

» 

• 

♦ 

Maggot 

1 “ , , , 

1 


3 » 

• 

c 

3 

1 

Magnate 

iK “ . . . 

» 


* * 

• 

> 

• 

’ ♦ 

Major 

1 % * . * , 

2 


» • 

• 

• 

4 

0 

Malay 

2 “ , , 

9 


» > 


» 

• 

0 

Malice 

2 % u , . , 

1 


> « 


* 

• 

3 

Mangle 

3 “ « 

> 


3 S 



* 

> 

Manly 

4 “ 

• 


• * 

9 




Marten 

c ** 

5 • • s 

9 


9 9 

3 




Master 

6 “ . 

• 


: . 

9 




Mastic 

8 “ . 

3 


> • 


O 



Mattock 

Ship via Express, . 

• 




0 



Worship 

“ “ Freight, . 

• 

• 

• 


• 

. 


Welkin 

Example. — Ship by express five 2-inch 
Malice Reducers.” 

reducing valves, 

“ Worship five 


Manufactured by the MASON REGULATOR CO., Boston, Mass. 





























ELECTRICITY FOR ENGINEERS, 


THE MASON ELEVATOR PUMP PRESSURE 
REGULATOR. 



This is a new pressure regulator, 
which we have designed especially 
for elevator pumps, the principal re¬ 
quirement of which is that upon the 
slightest drop in the water pressure, 
the pump shall start up to its full 
capacity. The fulcrum of the lever 
is a hardened steel knife edge, which 
makes its action as delicate as a pair 
of scales. Several large elevator manufacturers 
are now using these regulators with the best 
results. 

PRICE LIST. 


2 inch.$45.00 3! inch. $80.00 

2i “ . 55 °° 4 “ . 90.00 

3 “ . -jo.oo 


By a slight change in the interior mechanism, 
this regulator is made as a by-pass valve for ele¬ 
vator work. Prices same as above. 


For moving the rheostat switch on electric elevators, by the variation in 
water pressure we use the top part of this regulator mounted on a bracket. 
The rod which connects the regulating device with the steam valve is at¬ 
tached to the electric switch. Price $37.00. 


THE MASON VACUUM REGULATING VALVE. 



PRICE LIST. 


J inch. $18.00 

1 “ . 20.00 

ij “ . 23.00 

“ . 26.00 


This valve we designed and made at the 
request of a large sugar refinery, and it 
has proved very successful in regulating 
the vacuum. It is to a vacuum chamber 
what a reducing valve is to a steam-heat¬ 
ing system, in that it will keep a constant 
vacuum. One of these valves can be 
placed on the exhaust pipe from each one 
of a series of vacuum chambers; and al¬ 
though the same pump is used to exhaust 
from them all, yet a different vacuum may 
be kept in each one of the 
chambers. It is exceedingly 
sensitive. 


Manufactured by the MASON REGULATOR CO., Boston, Mass, 
































ELECTRICITY FOR ENGINEERS. 


ECH ANICAL BOOKS * * 


PUBLISHED BY 

Mason Regulator Company, 

BOSTON, HASS. 


These books are written by the best authorities on the subjects treated in 
clear and concise language. 

No. i. Key to Engineering. 92 pages. 30 
cents. 

A series of questions and answers giving practical ideas gathered from twenty- 
four years experience with the steam engine, by W. R. P.ailev ; also a chapter 
on the combustion of coal, by H. S. Williams. 

No. 2. Common Sense in Making and Using 
Steam. 60 pages. 25 cents. 

A practical book for the owners of steam plants, treating of economical 
management of the engineer department, by W. H. Bailey, M. E. 

No. 3. The Engineers’ Epitome. 135 pages. 
50 cents. 

Figures, fact's, and formula; for engineers. Contains formula; for various 
mechanical processes, with examples of working, by N. J. Smith of Hartford 
Conn. 

No. 4. Electricity for Engineers, -no pages. 
50 cents. 

A plainly written book in concise language containing just the facts which 
every engineer who has an electrical plant wishes to know. By Albert L. 
Clough, E.E. . Also all the rules of the Underwriters International Elec¬ 
trical Association for wiring. 

No. 5. Key to Engineering. (Third edition en¬ 
larged.) 174 pages. 50 cents. 

Containing additional chapters on water, heat, vapor, condensation, and 
vacuum; also a short treatise on electricity, by H. S. Williams. 

No. 6. Engineers’ Catechism. 182 pages. 
25 cents. 

This book has been for some time a standard work. It was written by 
F. E. Fowler, for engineers about to pass an examination. We have pur¬ 
chased the copyright, and now offer a new edition for one-half the former 
price. 









ELECTRICITY FOR ENGINEERS. 


STANDARD PRODUCTS 

OF THE 

Grosby Steam Gage & Valve Go. 


THE CROSBY IMPROVED STEAM GAGE 


is designed so as to give the greatest movement of the pointer with the least 
movement of the tube spring. By its peculiar design in this respect, the 
Crosby Gage is both more accurate and durable than any other make. 


CROSBY POP SAFETY VALVES 


for Locomotive, Stationary, and Marine Boilers, are a perfect protection 
from excess of steam pressure. 

The efficiency of the Pop Valve as compared with the common ball and 
lever valve, size for size, is 50^ greater in the former than in the latter. 

The Crosby Valves are fully approved by the United States Government. 


THE CROSBY WATER RELIEF VALVE 


is for the purpose of relieving all over-pressure of water in steam pumps, fire 
engines, hydrants, hose, etc. They are approved by the associated Factory 
Mutual Insurance Companies, and are fully guaranteed in every respect. 


THE ORIGINAL SINGLE BELL CHIME WHISTLE 


is manufactured only by this Company. This whistle has three compart¬ 
ments in one cylindrical bell, giving three tones which harmoniously blend 
into one. 


THE PATENT GAGE TESTER 


is a very simple and accurate machine for testing gages of all kinds, from the 
lowest to the highest pressure. 

This company manufactures a great variety of articles used in connection 
with steam on engines and boilers, all of which are of standard quality, and 
may be relied upon to do all that is claimed for them. The list comprises 
Pressure and Vacuum Gages of all kinds, used in the various arts, includ¬ 
ing Hydraulic, Compound, Combination, Pyrometer, Ammonia, and 
Test Gages; Test Pumps, Boiler Testing Pumps, and Air Pumps! 
Lubricators, Oil Cups, and Dynamo Oilers; Safety Water Gages, 
Common Water Gages, and Gage Cocks, Whistles, Whistle Valves, 
Etc., Etc. 


Main Office and Works at Boston, Mass., U.S.A. 


BRANCHES: 

NEW YORK, CHICAGO, and LONDON, ENG. 

a 


d 2 " m 
























r> 

</> ° 

^ ^ is . . o 

J o * X * 4 ° 0 N C 

* -f ^ C.° V . * ^yv .. ^. ' V 

3 *- ^ 





^ * /^ X "" s s ^ A c *b * y 

♦ ^ ** a' V A' * * 

\<% A* fmtttfe'+'Z 

*Pt. '" .< '>' Y 


** ,.„ ‘"’'V° ,../■= 2 - *AV /• 

s 0 /• .O' , *> s _ T // O ^ \» a. x * 0 

_ _, - 0 . M V y v >s 


*1 V*"/ ^ 

V ^ «#• 

0 o*‘ +■ *■ 

3 ' , \ 

V ^ ^ ,A v ^ 

^ ^ ^ * -v A^ ^ 

* ^ v< ^ ll 

Y - <*- % 










“ c $ : 

4 " jS? v s ^ % 

/ t 0 NC f ***** 

<* +f> 

S 

^ V 


* vv v * v 1 8 * ^b. 

^ A\ ^ 

^ Y 

* ^ 1 * 

* , 0 o^ J 

„■ A +**'> v 5 

” ' >^S ' •^ ' 1 %'' 5 " ° ’ v^\ < * • , %" * " ' ’ .O*' s 


£ <r 


\°°- 


3 ? <1 



, z 
^ 0 *W 

u «?%> * « 

y 0 v x "* -.O^ -r * / 

* 1 AV 


*b 0 ^ 0 * 

^ o 


^; 

> O A rt> >■ 

* Cj ^ 



«y* 


\ A ^ 
A'£k.\°° 


0 v K 



v V”'*> 0 V-^;% t 3 -* 0 ’ 0 ? 


Y ^ 



c^ ^ qV 

^ y 0 « x ^ ^0 , 

^ -f ^ r 0 v c 0 N c « *0 



























V * 


1 u u 






1 tr <r S \ 


% ° 

\ z 1/' 

° A^ ° 

* * ^ v <r^ u A 




<V> ■*<» «*•» 

^ *> 

%■ ' 0 * k ^ „ N c <y/ 4 ’^ . . s 

- ®o o 0 ’ .‘LI* v ^ , 

1° t _c*CV\YYwS«, ✓ *^i _\\ 

^" ’o o x : 

■> ^ -* 

«0’’ ‘-6 ’ » , „ o ’* .#' .0 

o> ^"r„-% ' * V > ,.*•», "> "' .-•., 


P V .- 

/ ^ a\ N 

<, ^ r * 


* 


.0 





s 

* v- •% 

„ * - - * ,v _ - 

„* c c, 

°- o 0 ' , c *. <p 



^ - <* ' '■" ' * ■’ •n*. V'lfra 

*'■>•'' ^ „v. t< 

•p . <<. ^nVOv'Ti'^jl ^ ^ A> v J? ; . . v?2, * 

y o o x ° a^rlBl* A v r flfe^ -■ *b o x 



/ s-^rv * sT ° v v * ’ * • , v *~ - *X ‘ 4 *- * 

J * jltQfoJ' ^ , r A SL 3 > „ * . *. V 

* JvsMP&k * r<’ -V. ^ rJ\ ^)(k- A, r ,/■> * 



v - ^ ^ 


* ,% 

0 « X * <6 

f 0 * c 0 "'’.♦, '*> 




































